expression, i-adjective
trivial; not a big deal; nothing serious
A set phrase meaning something is not important, not serious, or not worth worrying about. Often used to downplay a situation or to reassure someone.
See also: 大した事ない
この問題は大したことではないから、心配しないで。
This problem is not a big deal, so don't worry.
彼の言ったことは大したことで
What he said is nothing serious.
A negative form of the phrase 大したこと (a big deal), using the adjective 大した (great, considerable) and the noun こと (thing, matter). The negative ending ではない makes it 'not a big deal'.