This is a great question. I am probably getting it wrong, in the pure definition sense.

For me, a character actor is someone who plays a variety of a characters. They add texture and breadth to a story but are not necessarily the central character. They are the types who either, as you say, play a particular character over and over again... (I'm looking at you Walter Brennan and Pat Buttram) Or they disappear into roles, chameleon-like. (That's for you Jeffrey Wright!)

Huh. Wikipedia agrees with P-C:

A character actor is an actor who predominantly performs in similar roles throughout the course of a career. While some actors aspire to leading man or leading woman status, many notable actors have had enduring careers in less prominent, but important and memorable character parts. Character roles run the gamut from bit parts to secondary leads.

eta: There is something comforting about always knowing what you are going to get from a particular actor/character...but the designation doesn't really cover the actor who is so gifted range-wise, but doesn't take the center stage.

Adam Baldwin can play a lot of roles. He isn't a lead...whether by choice or not...and he works more, longer than most actors get to.

Is there a separate category for actors like that?

etaa: Forgive the obsession! Wikipedia adds some insight...'crossover actors', a term I never heard before:

Crossover actors

Many character actors have, however, gained star status; some have become widely known lead actors. Examples include Claude Rains, Dustin Hoffman, Gene Hackman, Kevin Spacey, Robert Duvall, Peter Lorre, Gene Wilder, John Malkovich, Ed Harris, Jack Black, Tom Hanks, Jack Nicholson, Don Cheadle, and Lynne Thigpen. Other character actors have developed a cult following with a particular audience as well, such as the fans of Star Trek, Doctor Who or The Rocky Horror Picture Show. This notwithstanding, a hallmark of many great character actors is that their names are not widely known yet their faces or voices are instantly recognizable; Paul Henreid, Sydney Greenstreet, or Barry Fitzgerald are some examples.

However, character actors are not limited to only seasoned performers, but also can refer to film directors who have either made the crossover to acting or worked in front of the camera before, such as John Huston, Sydney Pollack, Paul Mazursky, Mark Rydell and Tim Blake Nelson to name a few.

Personally, I look at Pollack, Mazursky and Huston, not so much as actors but as stunt casting. But that is probably because I 'study' cinema more than the average film-goer.

I once squeed over seeing Joel Schumaker on the street in NYC and my friends thought I was a freak for being able to recognize him.

Or they disappear into roles, chameleon-like. (That's for you Jeffrey Wright!)

Or, say, Gary Oldman.

Or, say, Gary Oldman

Perfect example.

Here's a character name I haven't seen on these lists yet, but is easily one of my favorites:

Ray Walston!

Seany - can you hop on IM for a seccy sec?

Ray Walston!

Poopdeck Papi!

David Warner
Tovah Feldshuh
Beth Grant (she played the stressed-out woman who tried to leave the bus in Speed and Jim Morris's mom in The Rookie)

I used to think it was an actor who always played a specific type of character, but then many people called "character actors" have had diverse roles.

I would call a character actor someone who plays secondary, but important roles. Often they're actors who disappear into roles, rather than call attention to themselves as an actor. They're usually not conventionally handsome, but they bring flavour to a role.

I think that wikipedia entry is fucked. It's got a modern idea of character actors confused into the idea of someone who plays a character type all their life, which you'd find more in commedia delle arte, or maybe older studio or repertory systems.

Also, it calls a lot of people character actors who've mostly been leading men: Tom Hanks, Laurence Olivier (?!?!) , Kevin Spacey, Jack Nicholson, Dustin Hoffman. I think Jack Nicholson is the antithesis of a character actor. He's always Jack, doing his thing.

I was just looking at Beth Grant's IMDB entry, and I completely missed the fact that she had been on Angel--in "Rm w/a Vu," she played Phantom Dennis's mom!