I. ˈtat verb
( tat·ted ; tat·ting )
Etymology: back-formation from tatting
Date: 1858
intransitive verb
: to work at tatting
transitive verb
: to make by tatting
II. ˈtat noun
Etymology: t rans- a ctivating t ranscriptional regulation
Date: 1985
: a small protein produced by a lentivirus (as HIV) that increases the rate of viral transcription and replication ; also : the viral gene that codes for tat