- 1 sideline somebody to prevent someone from playing on a team, especially because of an injury The player has been sidelined by a knee injury.
- 2sideline somebody to prevent someone from having an important part in something that other people are doing The vice president is increasingly being sidelined.
NAmE//ˈsaɪdlaɪn//[usually passive]Verb Forms present simple I / you / we / they sideline
he / she / it sidelines
past simple sidelined
-ing form sidelining