Purr, see UR.
URSE.
Nurse, curse, purse, accurse, disburse, imburse, reimburse, worse, verse, hearse, disperse, etc.
URST.
Burst, curst, durst, accurst, thirst, worst, first, versed, etc.
URT.
Blurt,§ hurt, spurt,§ dirt, shirt, flirt, squirt, wort,¶ vert,¶ etc.
US, or USS.
Pus,¶ us, thus, buss,§ truss, discuss, incubus, overplus, arquebus,† cuss,§ amorous, boisterous, clamorous, credulous, dangerous, ungenerous, generous, emulous, abulous, frivolous, hazardous, idolatrous, infamous, miraculous, mischievous, mountainous, mutinous, necessitous, numerous, ominous, perilous, poisonous, populous, prosperous, ridiculous, riotous, ruinous, scandalous, scrupulous, sedulous, traitorous, treacherous, tyrannous, venomous, vigorous, villanous, adventurous, adulterous, ambiguous, blasphemous, dolorous, fortuitous, gluttonous, gratuitous, incredulous, lecherous, libidinous, magnanimous, obstreperous, odoriferous, ponderous, ravenous, rigorous, slanderous, solicitous, timorous, valorous, unanimous, calamitous.
USE