ahead of one's time meaning

Having ideas, etc too advanced or progressive to be acceptable at the time

[American idiom]
having ideas or attitudes that are too advanced to be acceptable to or appreciated by the society in which one is living.
• People buy that artist's work now, but his paintings were laughed at when he was alive. He was ahead of his time.
• Mary's grandmother was ahead of her time in wanting to study medicine.

[American slang]
Fig. having ideas or attitudes that are too advanced to be acceptable in the present. (Typically: be ~; think ~.)
  Sue's grandmother was ahead of her time in wanting to study medicine.