Culinary definition of mince: To chop into very small, fine pieces.
C@H FOOD FOR THOUGHT
A helpful mental image to have when mincing food is one of tiny pieces of cracked wheat or bulgar. That granular size more-or-less represents the size of a mince. Minced garlic is sometimes called for in recipes and it is readily available as a prepared food in a jar.
With the exception of shallots and onion, not very many other foods are minced as a matter of course - and thank heavens for that. Chefs sometimes finely mince or ultra-finely dice red pepper or tomato shell as a garnish - looks gorgeous but is very time consuming.
Mince as a verb is not to be confused with mince as a noun - as in mince pies. Mincemeat for pies is a cooked mixture of dried fruit, spices, spirits and beef (meat and/or) suet baked into small (typically) pies. Old cook books sometimes refer to ground meat as 'minced' meat, but not so today.