freakish

prone to sudden illogical changes of mind, ideas, or actions had a freakish roommate in college who once decided to drive all the way to Canada on the spur of the moment Synonyms capricious, whimsical, impulsiveRelated Words impetuous, mercurial, moody, temperamental, volatile; crankish, eccentric, flaky, quirky; arbitrary, erratic, fickle, inconstant, irregular, shaky, willful (or wilful); impractical, quixotic, quixotical, romantic, unrealistic, utopian, visionaryNear Antonyms equable; down-to-earth, earthy, hard-boiled, hardheaded, levelheaded, matter-of-fact, practical, pragmatic (also pragmatical), reasonable, sensible, tough-minded; commonsensical, grounded, logical, no-nonsense, rational, sane, sober, sobersided, sound; fast, fixed, hard-and-fast, immutable, inflexible, invariable, unalterable, unbending, unchangeable uncompromising, unrelenting, unyielding; changeless, constant, established, set, settled, stable, steadfast, steady, unchanging, unvarying