1. Having three atoms; - said of certain elements or radicals 
2. Having a valence of three; trivalent; sometimes, in a specific sense, having three hydroxyl groups, whether acid or basic

Encyclopedia: Triatomic

• Mitterrand
• mittimus
• mitzvah
• Miwok
• mix
• mix in
• mix-up
• mixable
• mixed
• mixed bag
• mixed blessing
• mixed bud
• mixed doubles
• mixed drink
• mixed economy
• mixed farming
• mixed marriage
• mixed metaphor
• mixed nuisance
• mixed-blood
• mixed-up
• mixer
• mixing
• mixing bowl
• mixing faucet