A sick day that you take when you just don't feel like going to work or had too much to drink the night before.

'To pull a sickie'
Taking time off work under the false pretence that you are sick, when really you just can't be arsed to go in. Sickies also often pulled when hungover or when you've run out of annual leave.

someone who always fakes sick to get out of something

Something that would be considered sick or tight.

1, to fake illness to avoid work
2, to knee a guy in the crotch (it makes you feel like barfing)

A disgustingly overpowered (i.e. wordbroken/word) wordMagic: The Gathering/word card. Can be extended to other obscenely-awesome objects.
Related word: wordsickness/word

someone who is always messed up on drugs, or is addicted to them, does / sells them.

(often used in the 70's & 80's. RARELY used now.)