ugly duckling
uncle Tom Cobley and all
under a cloud
under arms
under fire
under no illusions
under siege
under starter's orders
under the auspices
under the radar
under the sun
under the weather
unring the bell
until the cows come home
up a blind alley
up and about
up for grabs
up in arms
up in the air
up the ante
up to no good
up to the mark
up to your neck
upper crust
upper hand
ups and downs
upset the applecart
upside down
use your loaf
BROWSE IDIOMS THAT START WITH LETTER "u"
A list of idioms in alphabetical order with definitions and examples