most ... ever; most ... up to now; more ... than ever before
Slang abbreviation of 過去一番 (かこいちばん). Used adverbially or as a noun to express that something is the most extreme in one's experience up to now. Often followed by an adjective or adjectival noun.
このラーメン、過去一うまい！
This ramen is the best I've ever had!
今日のテスト、過去一難しかった。
Today's test was the hardest ever.
Most common spelling; uses the kanji 一 for 'ichi'.
Variant using the numeral 1 instead of the kanji 一.
Katakana spelling for emphasis or casual style.
Abbreviation of 過去一番 (かこいちばん), literally 'past number one'.