also: きょういち
noun
today's best; best of the day
Colloquial abbreviation of 今日一番, used in casual conversation or social media to refer to the best thing that happened or was encountered today.
今日イチの笑顔をもらった。
I got the best smile of the day.
このラーメン、今日イチだね。
This ramen is the best I've had today, isn't it?
今日一番 is the full, more formal phrase meaning 'today's number one' or 'best of the day'. 今日イチ is a clipped, casual version used mainly in informal contexts.
Abbreviation of 今日一番 (kyō ichiban, 'today's number one'). The reading イチ comes from the on'yomi of 一.