Irrepressible means impossible to hold back, restrain, or suppress. When something is irrepressible, it bursts forth no matter what anyone does to stop it.

You see this quality most vividly in people whose energy, enthusiasm, or spirit simply cannot be contained. An irrepressible sense of humor means someone keeps making jokes even in serious situations where they're trying hard to stay quiet. An irrepressible optimist keeps finding reasons for hope even when circumstances look bleak. A child with irrepressible curiosity asks question after question, undeterred by tired sighs or “we'll talk about it later” responses.

Think of giggles during a solemn assembly: the harder you try to suppress them, the more powerfully they want to escape.

Irrepressible usually describes positive qualities: joy, creativity, determination, spirit. When historians describe someone as having an irrepressible spirit, they mean that person's fundamental character couldn't be crushed by hardship or opposition. An irrepressible grin can spread across your face despite your best efforts to look serious. That bounce-back quality, that refusal to be diminished, is what makes something truly irrepressible.