momentum /mō-menˈtəm/

1. The quantity of motion in a body measured by the product of mass and velocity
2. Force of motion gained in movement, impetus (informal)

• under the wire
• underthings
• underthirst
• underthirsts
• underthrust
• underthrusts
• undertime
• undertimed
• undertimes
• undertint
• undertints
• undertone
• undertoned
• undertones
• undertook
• under tow
• undertow
• under tow of vessels
• undertows
• undertrick
• under-tunic
• under-tunics
• under-turnkey
• under-turnkeys
• underuse