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

• urinary calculus
• urinary hesitancy
• urinary incontinence
• urinary organ
• urinary retention
• urinary system
• urinary tract
• urinary tract infection
• urinate
• urination
• urinator
• urine
• uriniferous tubule
• urinogenital
• URL
• Urmia
• urn
• urn fungus
• urn-shaped
• Urnula craterium
• urobilin
• urobilinogen
• urocele
• urochesia
• urochezia