When having a talk about deep matters and you don't want others to hear and abruptly someone comes to hear what your conversation is about.

The act of impeding in on a conversation, essentially killing any vibe that may have been present.

To change the subject at the request of a friend who doesn't want to discuss something uncomfortable in a large social setting. I.e. if someone brings up your friend's boyfriend and they just broke up, or her job and she just got let go, you talk-block and change the subject quickly.

To completely interrupt someone and talk about something else, for no apparent reason.

one step worse than a cock block. When a person interferes with other people getting acquainted. Talk blocks do not allow themselves to be elevated to the status of a cock block by ruining any chances before you even get to drop your name, leaving you shut down without the remote possibility of a sexual encounter, now or ever.

(V.) To stand in the middle of a group of people talking and face your back to someone, thus blocking that person from being in conversation.

verb:

occurs when one is trying to catch up with a friend and discuss dirt, but said friend's significant other enters the room and conversation must shift to "appropriate" topic so as not to upset the significant other or lead to unwanted interrogation. Significant other has "talk blocked" your conversation. Talk Blocker may also be any third party who walks into a conversation that the original parties do not want to share info with.