alternate - noun

someone who takes the place of another person

alternate - verb

• go back and forth; swing back and forth between two states or conditions
• exchange people temporarily to fulfill certain jobs and functions
• be an understudy or alternate for a role
• reverse (a direction, attitude, or course of action)
• do something in turns

alternate - adjective

• of leaves and branches etc; first on one side and then on the other in two ranks along an axis; not paired
• every second one of a series
• serving or used in place of another
• occurring by turns; first one and then the other

alternate - thesaurus

alternating   alternative   flip   interchange   jump   replacement   substitute   surrogate   switch   tack   understudy