1. Of a stimulus just strong enough to be consciously experienced 
2. At a threshold or transitional stage

Encyclopedia: Liminal

• underdo
• underdog
• underdone
• underdrawers
• underdress
• underdressed
• undereducated
• underemployed
• underemployment
• underestimate
• underestimation
• underevaluation
• underexpose
• underexposure
• underfed
• underfeed
• underfelt
• underfoot
• underframe
• underfur
• undergarment
• undergird
• underglaze
• undergo
• undergrad