Top Definition
Any extraterrestrial, most likely with some level of insanity and/or psychotic tendencies, that poses as the sister of any legitimate human. May emit, at any volume, the following: doggy voice, shrill sounds, nonsensical words, sudden shouts, low hissing sounds, extremely bad whistling, or other bizarre noises.
"Why is my little sister so annoying?" "She's probably an alien psycho sister."
by Cameo March 31, 2005

The Urban Dictionary Mug

Lotsa space for your liquids.

Buy the mug

The Urban Dictionary Mug

Lotsa space for your liquids.

Buy the mug

The Urban Dictionary Mug

Your favorite word on a white mug.

Create a mug

The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.

Buy the mug

The Urban Dictionary T-Shirt

Soft and offensive. Just like you.

Buy the t-shirt

The Urban Dictionary T-Shirt

Smooth, soft, slim fit American Apparel shirt. Custom printed. 100% fine jersey cotton, except for heather grey (90% cotton).

Buy the t-shirt