ligandPronunciation: /ˈlɪg(ə)nd/Definition of ligand noun Chemistry an ion or molecule attached to a metal atom by coordinate bonding. Biochemistry a molecule that binds to another (usually larger) molecule. Origin: 1950s: from Latin ligandus 'that can be tied', gerundive of ligare 'to bind'ligand in other Oxford dictionaries Definition of ligand in the US English dictionary