noun, noun or participle which takes 'suru', transitive verb
rash decision; jumping to a conclusion
Used for making a quick, often ill-considered decision or judgment without sufficient thought. Can be used as a noun or with する.
彼はいつも速断して失敗する。
He always makes rash decisions and fails.
速断は禁物だ。
Rash decisions are to be avoided.
即断 means 'instant decision' and can be neutral or positive, while 速断 implies a hasty, often negative judgment.
Compound of 速 (quick) and 断 (decide, judge). The exact historical derivation is uncertain, but the meaning follows naturally from the kanji.