indiscriminately; regardless of who it is; anyone and everyone
Used when an action is done without caring who the person is, often with a negative or critical tone. Common in phrases like 誰彼かまわず話しかける (talk to anyone and everyone).
He complains to anyone and everyone.
Please stop calling out to people indiscriminately.
手当たり次第 means 'using anything at hand' or 'haphazardly', focusing on objects or actions rather than people.
Standard kanji-kana mixed spelling.
Variant using the kanji 構 for かまわず.
A set phrase combining 誰 (who) + 彼 (he/that person) + かまわず (negative continuative of 構う, 'to care about'). Literally 'not caring who or what person', it became a fixed adverbial expression meaning 'indiscriminately (toward people)'.