Entirely means completely, with nothing left out. Entirely wrong, entirely different, not entirely.
Not entirely is the useful form: it concedes part of a point while withholding the rest, which is why it appears so often in careful disagreement. Entirely is stronger than largely and weaker than nothing else. Note entire, from the Latin for untouched, the same root as integrity.
1adverbentirelyCompletely, with nothing left out.
“I entirely agree with you; it's a terrible idea.”
entirely is an intensifier.
Also accepted in games: fully
Entire plus -ly, from Latin integer, whole or untouched. Integrity and integer come from the same wholeness.
Middle English
entyerly
English, today
entirely
From Middle English entyerly, entierly, enterely, entyreliche, equivalent to entire + -ly.
Etymology from Wiktionary, CC BY-SA