1. hi-vis - Noun
2. hi-vis - Adjective
hi-vis (comparative more hi-vis, superlative most hi-vis)
(of clothing) High-visibility.
hi-vis (uncountable)
High-visibility clothing.
All were organised and presided over by local volunteers wearing hi-vis vests. Source: Internet
Upon arrival, patients are marshalled not by NHS staff, but workers in hi-vis jackets supplied by outsourcing companies, such as Serco, G4S, Mitie and Sodexo. Source: Internet