Specifically meaning (and sometimes legally) that the item is literally
untouched by human hands.
The term comes from coins made at COIN
MINTS which were dropped from
the press directly into boxes for collectors and therefore never touched by human hands.
The meaning of the term "mint" is about as strict as the definition for the word "virgin."
In stretching the modern-day definition, it sometimes is valid to refer to an item which was purchased
brand-new and unopened, but has been opened and checked but never used.
A further stretch is the use of "near-mint" which would still mean something possibly tested and used briefly but which still has no evidence of human handling or use.
It does NOT mean "looks like it's almost new." It does NOT mean anything to do with the
herbal MINTS, as unfortunately assumed by many newer-generation mis-users of the term "mint."
It does NOT mean, in legal or historical use, anything to do with "looks cool" or "good" or "nice," as defined by other submissions on this website, on many ebay listngs and in common modern-day slang mis-use. That is sheer illiterate
bastardization of the term.
"This camera is
MINT condition, I opened it to see if it took the kind of storage-card that I use but it didn't, so I put it back
in the box."
"This 40-year-old
Gibson guitar has been in the closet since my grandfather won it in a contest, and other than a few playings it's nearly mint-condition."