spacer

Short definition from Wiktionary

Noun

1. 1
   A person who works or lives in space.
2. 2
   An object inserted to hold a space open in a row of items, e.g. beads or printed type.
3. 3
   A bushing.
4. 4
   A forgetful person; one who spaces out.
5. 5
   A type of add-on device used by an asthmatic person to increase the effectiveness of a metered-dose inhaler.
6. 6
   An instrument for reversing a telegraphic current, especially in a marine cable, to increase the speed of transmission.