Yes, nests is a Scrabble word!

Verb

1. Inhabit a nest, usually after building

2. Fit together or fit inside

3. Move or arrange oneself in a comfortable and cozy position

4. Gather nests

Noun

1. A structure in which animals lay eggs or give birth to their young

2. A kind of gun emplacement

3. A cosy or secluded retreat

4. A gang of people (criminals or spies or terrorists) assembled in one locality

5. Furniture pieces made to fit close together