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.
This ramen is the best I've ever had!
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'.