Going beyond all reasonable bounds; utterly senseless; extremely rash or reckless, wild; vehemently excited: = mad, adj. 5.

Of a person, action, disposition, etc.: uncontrolled by reason or judgement; foolish, unwise. Subsequently only in stronger use (corresponding to…

Of undertakings, actions, notions, statements, etc.: Going beyond prudent or reasonable limits; rashly or inconsiderately venturesome; going to…

Having or showing no more ‘brains’ or sense than a hare; heedless, reckless; rash, wild, mad. Of persons, their actions, etc.

Void of meaning or sense; foolish, silly, incoherent; also (of persons) light-headed, out of one's mind, delirious (cf. idle-headed, adj.). Obsolete.

Of the nature of a hare; mad, foolish.

transferred. Affected by wild and ungovernable excitement; ‘mad’ with rage, pain, grief, etc. †Also, in early use, applied as a term of reproach…

attributive or adj.= hare-brained, adj.

figurative. Madly foolish, frantic, idiotic, ‘mad’.

= lunatic, adj.

Chiefly English regional (northern and midlands). Out of one's mind, crazed; mentally deranged or deficient from senility; (in weakened use) stupid…

slang (originally U.S.). Of a person: liable to act in an odd or eccentric manner (as though exhausted or under the influence of drink or drugs)…

Foolish, crazy; mad.