na-adjective, noun
thoughtless; reckless; indiscriminate
Describes acting without careful thought, often leading to negative consequences. Used as a na-adjective or noun.
むやみに人を信用してはいけない。
You shouldn't trust people indiscriminately.
彼のむやみな行動が問題
His reckless behavior caused problems.
na-adjective, adverb taking the 'to' particle, noun
excessive; unreasonable; immoderate
Often used adverbially as むやみに or むやみと to mean doing something to an unreasonable degree or without good reason.
むやみにお金を使うのはやめなさい。
Stop spending money excessively.
むやみと大声を出すな。
Don't shout unreasonably loud.
やたら also means 'excessively' or 'indiscriminately', but is more casual and often used in spoken language. むやみ carries a stronger nuance of thoughtlessness or lack of reason.
無茶 means 'unreasonable' or 'absurd', often implying something is beyond reasonable limits or physically impossible. むやみ focuses more on the lack of careful thought or moderation.
The origin is uncertain. The kanji 無闇 and 無暗 are ateji, combining 無 (without) with characters for darkness, suggesting 'without clarity or reason'.