The act of sending a sexual text message to someone by attaching a picture of hair that arouses them. Only works for kinky freaks who can be aroused by their partner's hair, particularly when it's in an unusual or unnatural state.
Guy: Baby, you know what you should send me that'll really turn me on!?
Girl: What? Sext
you a sexy nude shot?
Guy: No. Hext me a picture of your crazy bed hair when you first wake up in the morning... I love it when that shit is messy sticking up all over the place!
Girl: Damn you're such a freak...