Illustrated Glossary of Organic Chemistry

Protonate: To transfer a proton (a hydrogen atom) to another ion or molecule. The forms the conjugate base of the proton donor, and the conjugate acid of the proton acceptor.

Protonation of water by sulfuric acid forms bisulfate ion (the conjugate base of sulfuric acid) and hydronium ion (the conjugate acid of water). In the reverse process, hydronium ion protonates bisulfate ion.