Official meaning of "tacatá"
1. m. Andador metálico con asiento de lona y ruedecillas en las patas, para que los niños aprendan a andar sin caerse.
Metalic walker with a seat made of canvas with small wheels on its legs, for the children so that they learn to walk without falling.
However, because of the song tacata, it can mean whatever the context of the use is...for example, esa chica es tacata (girl is hot/sexy/whatever); it can also mean to have sex, as in, vamos hacer tacata (we are going to "do it") or estaban haciendo el tacata (they were having sex). Matter of fact, some friends even use it to mean, girl is untouchable. Really, you can attach whatever meaning you want to it with your friends.