to react with less emotion, force, or intensity than is appropriate or expected
intransitive verbun·der·re·act·ed, un·der·re·act·ing, un·der·re·acts
To react with insufficient enthusiasm, force, or emphasis.
(third-person singular simple present underreacts, present participle underreacting, simple past and past participle underreacted)
- (intransitive) To react inadequately.
under- +"Ž react