redshirt

noun

• 1US informal a college athlete who is withdrawn from university sporting events for a year to develop their skills and extend their period of playing eligibility by a further year at this level of competition: [as modifier]:a redshirt freshman who had never started a college game and wasn’t expecting to start in one this year

• 2a supporter of Garibaldi, in particular one of the thousand who sailed with him in 1860 to conquer Sicily.

verb

• keep (an athlete) out of university competition for a year:he was less developed at the outset, so he was redshirted
• [no object] (of a college athlete) be barred from university competition for a year:he redshirted last season