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

• parametritis
• parametrization
• parametrize
• paramilitary
• paramilitary force
• stair
• stair-carpet
• stair-rod
• staircase
• stairhead
• stairs
• stairway
• stairwell
• stake
• stake driver
• stake race
• stakeholder
• stakeholder society
• stakeout
• stakes
• stakes race
• stalactite
• stalag
• stalagmite
• stale