How to say "erratic" in Japanese

• 突飛とっぴ
  na-adjective, nounCovers 'erratic' as wildly unconventional or offbeat: ideas, plans, or behavior that startle by departing far from the ordinary. Typical context: reacting to a bold, offbeat proposal or an unconventional way of doing things.
  君きみの行動こうどうは突飛とっぴすぎるよ。↗

  Your behavior is too extraordinary.
• 発作的ほっさてき
  na-adjectiveCovers 'erratic' as fitful or spasmodic: actions or movements that come in sudden, unpredictable bursts rather than continuing steadily. Typical context: someone who acts on sudden impulse, unpredictably and without warning.
• 常軌を逸したじょうきをいっした
  expression, prenominal modifierCovers 'erratic' as aberrant: behavior that has left the normal track, going beyond the bounds of ordinary conduct or reason. Typical context: conduct so outlandish that it seems to have gone off the rails.
• 心もとないこころもとない
  i-adjectiveSeldom the word you want for 'erratic': it really means unreliable or undependable — people or things you cannot count on, leaving you uneasy. Choose it only when 'undependable' is the sense you mean.
  あの人ひとの言いうことはどうも心こころもとないわね。↗

  I cannot place confidence in his words.

All four are less common renderings: pick 突飛 for wildly unconventional ideas or behavior, 発作的 for fitful, burst-like actions, 「常軌を逸した」 for conduct gone beyond normal bounds, and 「心もとない」 only for the 'undependable' sense.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 突飛とっぴerratic
• 発作的ほっさてきspasmodic
• 常軌を逸したじょうきをいっしたaberrant
• 心もとないこころもとないunreliable