Is waif a word in the Scrabble Dictionary

Yes, waif is playable

...and is worth 10 points.

Found in the following dictionaries

Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)

"Waif" Definition

noun

A homeless person, especially a forsaken or orphaned child.
An abandoned young animal.
Nautical See waft.
Something found and unclaimed, as an object cast up by the sea.
A piece of property found (as washed up by the sea) but unclaimed.