It's the imperative form of the verb "tragar", which means "to swallow".
Here are some examples:
* "Traga" la medicina. (Swallow the medicine.)
* "Trágalo" de una vez. (Swallow it all at once.)
It's important to note that "tragalo" can also be used as a slang term in some Spanish-speaking countries. In those cases, it can be used to mean "to accept something, even if you don't want to."
For example: "Te lo tragas, aunque no te guste." (You swallow it, even if you don't like it.)
The meaning of "tragalo" will be clear based on the context of the sentence.