Upon noticing one has received a text, the hypothesis one makes regarding who it was that just texted them, prior to checking the phone for confirmation or contradiction.
It only counts if the message guessed upon is the first of a conversation.
Example 1:
*Bzzzt*
John: "Man, I bet that's Ryan texting me."
Evan: "Really? Why?"
John: "I was talking to him before today about hanging out."
John: *checks phone*
Evan: "Was it him?"
John: "Yeah."
Evan: "Nice text-guess, man."
*Bzzzt*
Alex (in thought): "That better not be Jena texting me.
Damn it, I know it's going to be her."
Alex: *checks phone*
Alex: "AH, SHIT!"
James: "What's up?"
Alex: "It was Jena, again. I text-guessed it and everything, too."
1: When you are guessing or think you know the answer, but are uncertain.
2: You have absolutely no idea, so your just picking an answer at random.
3: Predict or estimate without sufficient information.
1: But let's take a wild guess here: many mothers do the same!
2: Anything beyond that would be a wild guess, especially when one considers that mobile cellular and the Internet barely existed two decades ago.