Sexual orientation is a large part of online dating; as such, a whole plethora of acronyms have emerged.
BIM stands for bi-sexual male.
Larry had traditionally searched for gay men on Seeking.com. One day, he decided to search for bisexual males, thinking it might increase the number of guys he could potentially date. During his search, he found lots of guys with the word 'BIM' in their profile description which let him know he was on the right track!