Interchangable with monged or monged out."Bonged out" is the state you are left in after partaking in the prolonged inhalation of combusted canabis (herbal or hash) smoke & vapour drawn up through water in a smoking device known as a bong. See mongathon and bongathon.
After smokin' that rope bar we was totally bonged out, innit see! I couldnt even see the fucking Playstation!