at sight

[at sight] or [on sight] {adv. phr.} 1. The first time the person or thing is seen; as soon as the person or thing is seen.

Firstgraders learn to read many words on sight.

Mary had seen many pictures of Grandfather, so she knew him on sight.

Compare: AT ONCE(1). 2. On demand, on asking the first time.

The money order was payable at sight.