arm ‧ band /ˈɑːmbænd $ ˈɑːrm-/ BrE AmE noun [countable]
1 . a band of material that you wear around your arm to show that you have an official position, or as a sign of ↑ mourning
2 . [usually plural] British English one of two bands of plastic filled with air that you wear around your arms when you are learning to swim SYN waterwings