It is or was used as a grapheme in some languages of Vanuatu, such as North Efate, South Efate and Namakura, to represent a sound [k͡p], like the ⟨c⟩ in "cat" and ⟨p⟩ in "pay", pronounced simultaneously.
In Bislama, the lingua franca of Vanuatu, p with tilde is called snekpi "snake-P".
In standard HTML code: majuscule P̃, minuscule p̃.
The Unicode HTML hex code is: minuscule p̃, majuscule P̃.
The Unicode HTML decimal code is: minuscule p̃, majuscule P̃.