u-boat, a: a "sub" in a football match
Source: GTH

Ullo dir! Greetings; I am pleased to make your acquaintance.
Source: LS1

ultraviolence (as in "He was so annoyed that his face went all ultraviolence): a LIverpudlianism for an enraged reaction.
Source: SL

uncle's cards(obsolete): a family euphemism for pledge tickets for pawned material
Source: MEM

under the arm, to be: to be feeling poorly
Source: LS1

under the counter work:  work done for an undeclared income, to avoid taxes, or other complications of reporting.
SL

Under de lamp(dockers): It's under de lamp--It is payment less than the rate for the job.
Source: LS1

Unkill. De unkill. My uncle.
Source: LS1

unlucky finger, to be an:  to be someone who is always unlucky, a Jonah.
Source: JML

high jump, to be in for the: (some sort of severe civil penalty)
Source: JML

up in one's nightshirt, to be: to be crazy, nonsensical
SL

up hill, to give someone : to lord it over someone
Source: SL

Up ther shute: in serious trouble
Similar phrases: up ther cooee, up ther drain, up de spout, etc.
Sources: LS2, Moloney

Up ther pole: crazy, irresponsible
Source: LS2

Up der broo (beroo, brow): up the hill
Source: LS1

Up-de-entery eyes. She got up-de-entery eyes. She has a come-hither look. According to Spiegl, "entery" refers to the narrow alleys typical of much nineteenth century urban housing, where much of the courtship would take place.
Source: LS1

Upper Parly. Upper Parliament Street. Spiegl notes a tongue- twister practiced by Liverpool children: "I'll chase a pup up Upper Parly."
Source: LS1

Urdu. Mind me Urdu! Do not ruffle my coiffure.
Source: LS1

urgent note, to be on: to be on the critical list of a hospital
Source: LS1

Urry-up cart: the "Black Maria" police van.
Source: LS1

Us: I; me.
Source: LS1

Utney: children's leap-frog
Source: ML