Not usual for that person or that thing — and so a little surprising. "He spoke with unwonted warmth." "There was an unwonted silence in the classroom."

Here is the part worth slowing down for: `unwonted` does not mean "rare in the world." It means "rare for this one." If your strictest teacher smiles, that smile is unwonted — smiles are common enough everywhere, just not from them. The word measures against a habit, not against the whole world. That is why it so often sits beside words for feelings and manner: unwonted kindness, unwonted energy, unwonted care.

Be honest about how old this word feels. It is literary and rather old-fashioned; most native speakers today would write `unusual` or `uncharacteristic` instead. You will meet it in novels, in older writing, and in reading exams — and almost never in conversation. Knowing it is a reading word, not a speaking word, will save you from sounding strange.

It goes before a noun (unwonted patience). Saying "his patience was unwonted" is grammatical but sounds stiff even in books.