short term used for "3 for 10" when dealing with weed. Mainly in Houston and surrounding cities dealers sold sweets (pre rolled marijuana cigars) and to cut out the competition the had deal such as 5 for 20 and 3 for 10. This can be heard in older Texas rap as the threefa deals are hard to come by since the raising of tobacco prices.
"lets go get a threefa, them hoes better be fat"- Lucky Luciano
"Put a 3 for 10 in the wind" - Lil Bing