Green’s Dictionary of Slang

(US drugs) a sixteenth of an ounce of a given (powdered) drug.

1994		J. Wambaugh Finnegan’s Week 50: My brain got fried from snortin all that crank. Used to do a teener every night.
2002		J. Lerner You Got Nothing Coming 203: Quarters, teeners, eight balls, whatever the customer wants.