tat

1. :  a small protein produced by a lentivirus (such as HIV) that greatly increases the rate of viral transcription and replication and enhances the susceptibility of T cells to infection; also :  the viral gene that codes for the tat protein

chiefly US slang

1. :  a tattoo on a person's skin He pulls up his shirt to show us his tats. — Dave Eggers

chiefly US slang

1. transitive verb

2. 1 :  to mark or color the skin with tattoos :  tattoo The benefit of getting tatted at a festival is that you have more than 200 artists from which to choose. — Kellie Hwang —often used with up … say you're not a gang member, yet hang out with gang members, get tatted up with gang symbols or nicknames … — Kimberly Edds

3. 2 :  to mark (something) with something like a tattoo Cargo trains, all rusted and tatted with graffiti, occasionally pass on the neighboring track. — Kara Starzyk —often used with up My passport got tatted up pretty good this year. I hit a dozen countries on five continents, as well as eight states. — The Chicago Sun-Times

1. thematic apperception test

1. 1:  a small protein produced by a lentivirus (as HIV) within infected cells that greatly increases the rate of viral transcription and replication and that is also secreted extracellularly where it plays a role in increasing viral replication in newly infected cells and in enhancing the susceptibility of T cells to infection—called also tat protein

2. 2:  the viral gene that codes for the tat protein

1. thematic apperception test