spigot

1. Plumbing. Where the water comes out.

http://www.cumberlandcd.com/rainbarrel.html

2a. Lighting. Piece of attachment hardware commonly found on studio lighting fixtures to provide a wider range of mounting options than the theatrical C-Clamp.

http://www.doughty-engineering.co.uk/cgi-bin/trolleyed_public.cgi?action=showprod_G1193.

2b. May also (loosely) refer to the part of a theatrical c-clamp that the yoke bolt threads into.

3. Rigging. An alternative truss end design to bolt plates, the "fork and spigot" is arguably faster and stronger.