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.

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.

• (UK) A hand tool for adjusting nuts and bolts.
  
• (Weapon) A hand tool shaped like a small crank handle, for winding the spring of a wheel lock on a musket.
       Quotations
       *1786: Fig. 10. The spanner for spanning or winding up the spring of the wheel lock. — Francis Grose, A Treatise on Ancient Armour and Weapons, page xvi.
  
• (idiom) (UK) A problem, dilemma or obstacle; something unexpected or troublesome
        Half way through the production of Macbeth, the director found that the stage was smaller than he expected. This really threw a spanner in the works.
  
• (UK, mildly derogatory) A stupid or unintelligent person; one prone to making mistakes, especially in language.
        You spanner, Rodney! I wanted a Chinese, not an Indian!