Spanner \Span"ner\, n.

1. One who, or that which, spans.

2. The lock of a fusee or carbine; also, the fusee or carbine itself. [Obs.]

3. An iron instrument having a jaw to fit a nut or the head of a bolt, and used as a lever to turn it with; a wrench; specifically, a wrench for unscrewing or tightening the couplings of hose.

4. pl. A contrivance in some of the ealier steam engines for moving the valves for the alternate admission and shutting off of the steam.

Source: Webster's Revised Unabridged Dictionary (1913)