1. Off work, but available to provide a service if requested
   "I'm on call for my patients 4 days a week and every fourth weekend"

Encyclopedia: On call

• undergo
• undergrad
• undergraduate
• underground
• underground press
• Underground Railroad
• Underground Railway
• undergrow
• undergrowth
• underhand
• underhanded
• underhandedly
• underhung
• underivative
• underived
• underlay
• underlayment
• underlet
• underlie
• underline
• underling
• underlip
• underlying
• undermanned
• undermentioned