An Oxymoron is a combination of contradictory words. If you describe a dog as "pretty ugly", you have used the oxymoron "pretty ugly". "Pretty" means the opposite of "ugly".
Here's a bunch of Oxymorons, which I took from:
absolutely unsure almost exactly alone together authentic replica
awful good bad health bankrupt millionaire big town
black heart black light bland spice blank dictionary
boring entertainment boyish grandpa bright night bright rain
buried alive calculated risk calm wind civil war
clean boy clean dirt clogged drain cold fever
completely destroyed completely unfinished cooked sushi criminal cop
dark day deafening silence death benefit definite maybe
devilish angel different pattern distant relative down elevator
dry ice dry snow dull knife dull needle
educated guess expected surprise express line false hope
fast food fast snail fast walk firm pillow
flying fish freezer burn friendly enemy friendly fire
future history gentle turbulence giant dwarf good grief
grateful dead Great Depression grounded airplane half empty
half full hard cushion high ground huge shortage
icy hot ignorant professor incredibly dull inside out
jumbo shrimp large ant long shorts loose knot
loose tights loud whisper lover's quarrel low-rise
master slave mean smile missing present near future
near miss new antique night light night vision
non-working mother old newborn old news opposite attraction
organized chaos original reproduction paper towel partially destroyed
past prediction peasant king peer pressure perfect idiot
perfectly ridiculous plastic glass pleasantly confused positively negative
positively wrong presently gone problem solved pretty ugly
pure dirt quiet noise quiet riot random order
relative stranger restless sleep round corner sad clown
sadly funny sad smile same difference serious comic
silent alarm silent scream silent speech sit up
slow jet slow jog slow speed small crowd
small giant soft rock soft thunder spoken thought
student teacher study break stunted growth stupid genius
sure bet sure guess sweet sorrow sweet tart
talking mime talk show tame beast terribly nice
thunderous silence tiny mountain unknown knowledge usually unusual
virtual reality warm ice weak muscle wheeled walker
white night wickedly good wild dog working vacation
Compound Oxymoron Words:
bittersweet color-blind dimwit doorstop
homework lightweight seashore spendthrift
understand weekday
Rod P.