A cellular telephone obtained with the specific intent of calling or texting a love interest. The need for a Booty Phone occurs when two people hook up and find they have different cellular providers. Rather than pay overage charges, it is less expensive to add a Booty Line to one's cell phone plan.
Dylan: "Allison and I decided to get a Booty Phone."
Oscar: "Whose network did you choose?"
Dylan: "Hers...ten bucks a month with unlimited network calls...although textual relations still cost extra. The phone was only 20 bucks plus tax."
A phone purchased in secrecy from a carrier other than the one your gf or wife knows about. Used specifically for booty calls. A number you can give out freely without fear of getting caught.
Last night I took a shower and my gf read my text. I gotta get a booty phone!
I got to work Monday and had four voicemails on the booty phone.