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

• Wayland the Smith
• waylay
• waylayer
• wayleave
• waymark
• Wayne
• Wayne Gretzky
• waypoint
• ways
• ways and means
• Ways and Means Committee
• wayside
• wayward
• waywardness
• wayworn
• wazzock
• Wb
• WBC
• WbN
• WbS
• we
• we're
• we've
• weak
• weak force