Definition of "underact" []

• To perform (a role) weakly or with insufficient expressiveness. (verb-transitive)
• To understate (a role) intentionally; underplay. (verb-transitive)
• To perform in an understated way. (verb-intransitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A fine British cast overact or underact in this perfunctory true-life tale of a working-class lad from a sink estate in south London."
• "I spent my youth anesthetizing myself just enough to stand the daily less-violent silent injustices, and I think it means I tend to underact when the hatred is more open."
• "There are a grand total of two scenes where Kristen Stewart does NOT underact, and the hospital scene is absolutely brilliant in my opinion."