un·bound1 / ˌənˈbound/ • adj. not bound or tied up: her hair was unbound | fig. they were unbound by convention. ∎ (of printed sheets) not bound together. ∎ (of a book) not provided with a proper or permanent cover. ∎ Chem. & Physics not held by a chemical bond, gravity, or other physical force: unbound electrons.un·bound2 • past and past participle of unbind.