This is an expression commonly used to signal to another party that either a) you no longer want to text them, or b) you intend on hanging up. This is a smooth way to avoid answering or hearing things from other people.

However, sometimes, it's true, and the person's phone really is about to die. This is rare.
(speaking on the phone)
Katie: So I've really been thinking about you a lot. I think I might love y-
Michael: Oh, shi*, sorry, my phone's about to die! -click-

Chelsea: Myfriend Kyle said he really digs u. what did u think about him?
Sam: sry my phones about 2 die
by evil_gumball April 17, 2011
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You, “My phone is about to die”
Anyone in your house “Well charge it!”

When your phone is on low percentage battery and you need to charge but feel hungover from last night and scream “MY PHONE’S ABOUT TO DIE!!!!”
by My phone’s about to die August 02, 2019
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