I think, based on the question (which is slightly ambiguous) that the word would be מומר literally "someone who exchanged" (Judaism for something else).
This term is used to refer to someone who doesn't follow the Torah rules.
There are two general terms:
1) מומר לתאבון -someone who breaks the rules habitually out of desire.
This person knows that a particular action is wrong (i.e. eating cheeseburgers) but the temptation is so strong that they habitually give in. This type of person would keep the laws if given the option; i.e. if there was both kosher and non-kosher meat available, they would choose kosher. But if there was no other meat available, they would eat the non-kosher.
2) מומר להכעיס a rulebreaker in order to "anger" G-d. This person doesn't care about the Torah and willfully rebels against it. Even given a kosher option this person would choose the non-kosher out of spite.
These two types would relate to being "Anti Torah" in action, and in belief, respectively.
This term comes up many places is the Talmud and Halacha. One of the main central places that it is discussed is in Hilchos Shechita, the laws of slaughtering animals, since certain types of mumerim cannot shecht.
See the first 6 daf of Maseches Chulin and Shulchan Aruch Y.D. 2 for specific details nuances about "mumerim.
As mentioned in a comment, censors did change lots of the text in the gemara and rabbinic literature.
Specifically, they often interchange the words "mumar" (someone who is 'anti-Torah') "min" (heretic) "goy" (non-Jew) and "akum" (idol worshipper.)
There is sometimes disagreement about whether a source is referring to one category or another.
So be aware when trying to research this topic that there is confusion and disagreement on occasion.