shoulder check

Short definition from Wiktionary

Verb

1. 1
   To look backwards over one's shoulder while driving or biking, before changing lanes or making a turn, to see if any vehicles are in one's blind spots.
2. 2
   To check (strongly bump into) with one's shoulder(s).

Noun

1. 1
   An instance of looking backwards over one's shoulder while driving or biking, before changing lanes or making a turn, to see if any vehicles are in one's blind spots.
2. 2
   An instance of checking (strongly bumping into) with one's shoulder(s).