1. [adv]  under the feet; "trampled the beans underfoot"; "green grass growing underfoot"
2. [adv]  in the way and hindering progress; "a house with children and pets and toys always underfoot"

UNDERFOOT is a 9 letter word that starts with U.

1. \Un`der*foot"\, adv.
   Under the feet; underneath; below. See {Under foot}, under
   {Foot}, n.
   
   

2. \Un`der*foot"\, a.
   Low; base; abject; trodden down.