Definition of underact in US English:

underact

verb

[no object]
  • Act a part in a play or film in an overly restrained or unemotional way.

    • ‘I think this movie may mark the only time in recorded history when he managed to underact in a part.’
    • ‘He was often, and probably justly, accused of underacting in the movies, but never of overacting.’
    • ‘DeNiro underacts brilliantly, creating a character whose obsessive concern for control and order is both his means to the top and his undoing.’
    • ‘Who overacted, underacted, didn't try or couldn't act his or her way out of a paper bag?’
    • ‘When in doubt, they seem to choose underacting, which is a smart pick.’
    • ‘This movie is loud, gaudy, underacted, and completely without a soul.’
    • ‘The young actress manages, at the same time, to underact and overdo playing a grieving yet bratty young girl.’
    • ‘Thank John, who overacts in direct proportion to the amount of underacting everyone else does.’
    • ‘An actor himself, he doesn't write plays so much as actors' exercises: violently angry confrontations, absurdly bizarre vignettes, and abject deflations good for practicing sotto voce underacting.’
    • ‘For once, he underacts, and still manages to create a memorable character.’
    • ‘He underacts many scenes, perhaps going for stoic emotional pain but looking bored.’
    • ‘It's a caper film, with all the obligatory touchstones of the genre and everyone underacts to great effect.’
    • ‘The acting isn't all that way, because we're sometimes treated to underacting as a change of pace.’

Pronunciation

underact

/ˌəndərˈakt//ˌəndərˈækt/