Entry 1 sense Webster, 1913 Rashness · Rash·ness · IPA 01 n. The quality or state of being rash. 1. The quality or state of being rash. “We offend . . . by rashness, which is an affirming or denying, before we have sufficiently informed ourselves.” — South. Syn. Temerity; foolhardiness; precipitancy; precipitation; hastiness; indiscretion; heedlessness; inconsideration; carelessness. See Temerity.