U0056600 (ŭn′dər-rē-ăkt′)intr.v.un·der·re·act·ed, un·der·re·act·ing, un·der·re·acts To react with insufficient enthusiasm, force, or emphasis.un′der·re·ac′tion n.
underreact
(ˌʌndərɪˈækt) vb (intr) to react with less intensity than is expected or is suitable