Terrying is when somebody leaves in mid sentence without informing the other speakers.
Usually this happens online or when speaking with the blind.
It is considered rude to do such a thing, so the term "Terrying" has come into place.
Bill was Terrying before he came back from being afk.
John couldn't believe Bill was Terrying.
John: "I can't believe you were Terrying on me!"
Bill: "I was Terrying? Sorry I forgot to tell you"