Noun
U-bend (plural U-bends)
A U-shaped bend, usually the bend in a waste pipe.
Synonym: return bend
Additional tubing connects the slide to the bell of the instrument through a neckpipe, and bell or back bow (U-bend). Source: Internet
However, as the lower-pitched instruments would be unacceptably long if straight, for ergonomic reasons, the larger instruments usually incorporate a U-bend ("bow") at, or slightly above, the third-lowest tone hole. Source: Internet
With the other hand form a small loop in the remaining section and draw it over the U-bend so that the loop forms a half hitch and stays there if the free end of the rope is pulled taut. Source: Internet