The definition of an NHL agitator is a varied one. Is it a player who can pester opponents while putting up points? Is it someone who tries to draw penalties by getting under the opposition's skin? Is a true agitator willing to drop the gloves, or are they more likely to shy away from fighting to further infuriate their foe?

To paraphrase what Supreme Court Justice Potter Stewart once said in a censorship ruling about a hard-core pornography: it's hard to define, but I know it when I see it. So determining what an agitator does is subjective, but we know them when we see them. And this year, a lot of the league's top trouble-makers seem to have lost their way. Here's a look at who I consider (in alphabetical order) the top 10 agitators in the NHL, and the season's they're having.

Sean Avery, New York Rangers — Remember when Avery not only drove opponents crazy but also chipped in with double-digit goals? No more. A two-time 15-goal scorer, Avery has just one goal this season and is on pace for 252 penalty minutes. Avery twice broke the 250-minute penalty barrier when he was with the Kings, boosted by 14 and eight fights in those two seasons. When Avery was at his best with the Rangers, he was usually refusing to fight and drawing penalties. Just 40 games into the 2010-11 season, Avery has seven fights (his most since he had those eight back in 2005-06) and he hasn't been anywhere near as effective. Grade: D

Dave Bolland, Chicago Blackhawks — Bolland doesn't bug opponents with fights or constant body checks, but rather an active stick and mouth. Count the Sedin twins and Joe Thornton among those who have boiled over at Bolland's antics. With the massive roster turnover in Chicago, Bolland was one of the players that many thought could boost his offensive numbers to pick up some of the scoring slack. While the 24-year-old's numbers aren't off what he did in an injury-riddled campaign last season, he is nowhere near the 19-goal, 47-point player he was in 2008-09. Grade: B-

Alexandre Burrows, Vancouver Canucks — Burrows became one of the NHL's top talented pests over the past two seasons by scoring a combined 63 goals and amassing 271 penalty minutes. But a shoulder injury led to offseason surgery that cost him 10 games to start the year. In 28 games, Burrows' scoring is down (eight goals, 11 assists) and he has just 11 penalty minutes. The Canucks are still winning, but Burrows is at his best when he's producing and pestering. Grade: B

David Clarkson, New Jersey Devils — Clarkson has been an unheralded part of New Jersey's success the past few seasons, but his 2010-11 mirrors that of the bottom-feeding Devils. After going nine games to start the season without a goal, Clarkson is now in a 17-game goalless drought. His minus-18 is among the league's worst (along with several other Devils, to be fair) and anyone who thought Clarkson had 20-goal potential is now wondering if he can even get 10. Clarkson is still hitting (team-high 80) and fighting (seven), but his ability to both agitate and score is, for now, a distant memory. Grade: D

Matt Cooke, Pittsburgh Penguins — Some would say Cooke is not an agitator, just a dirty player. Perhaps, but every agitator gets the "dirty" moniker at some point. Cooke leads the Pens in hits (115), is tied for fifth in points (18) and continues to drive the opposition crazy. Sounds like successful agitation to me. Grade: A-

Steve Downie, Tampa Bay Lightning — Last year, Downie was the NHL's only 20-20-200 player, finishing with 22 goals, 24 assists and 208 penalty minutes. The last time someone did it? Theo Fleury (24-39-216) in 2001-02. But the 2010-11 has been one injury after another for Downie. First he missed time with a back injury, then went to injured reserve because of a bad ankle. He has just three goals in 24 games this season. Grade: C-

Patrick Kaleta, Buffalo Sabres — Kaleta is a fourth-line agitator, getting limited minutes to ply his craft. He is unlikely to ever put up big points, but he again leads the Sabres in hits (89) and his pummeling of Derek Dorsett was one of the most one-sided fights of the year. Grade: B+

Maxim Lapierre, Anaheim Ducks — Lapierre regressed last season after scoring 15 goals in 2008-09, managing just seven for the Habs. Lapierre was rumored to have approached the Canadiens for a trade because he was disappointed with his role and ice time, and he was shipped to Anaheim Dec. 31. Lapierre, who led Montreal in PIMs before the trade, is expected to take on a bigger role in Anaheim, especially with Ryan Getzlaf on the shelf. Grade: C

Steve Ott, Dallas Stars — One of the more curious signings in the post-lockout NHL was Dallas adding Avery when they already had Ott. The 28-year-old has surpassed Avery as the game's best-known disturber, keeping a 20-goal pace and still agitating like no other. As Eric Lindros once said about playing with Claude Lemieux and Brendan Shanahan on Team Canada, "Anyone I can't stand to play against, I would like to play with." The rest of the Stars are surely glad it's Avery, not Ott, who is gone. Grade: A

Jarkko Ruutu, Ottawa Senators — Ruutu had his best statistical season with the Sens last year, posting career highs in goals (12) and points (26), but 2010-11 has been disappointing for the aging agitator. He has hit a low of late, spending the past two games as a healthy scratch after playing all 82 games last season. Trade speculation has started to swirl around Ruutu, who is in the final year of his contract. Grade: D