An overacting actor or a performance that is over-the-top. Often characterized by using too much volume when speaking, making theatrical gestures or overemphasizing big emotions. Hammy actors are not necessarily bad actors - what can be regarded as charismatic in one context can easily become hilarious in the wrong one.
Brian Blessed,
Vincent Price and William Shatner are prime examples of hammy actors. Can also be used as a verb:
hamming.
Although doing his best to serve the film's low key atmosphere,
Vincent Price can't help relapsing into his hammy mannerisms at times.
Within the bizarre world of Flash Gordon,
Brian Blessed can pile on all of his hilariously charismatic overacting, without fear of being perceived as hammy.
Star Trek is in many respects a ground-breaking series in the genre of sci-fi, but decidedly marred by William Shatner's
hamming.
