Boojoint is synonymous to the words "boo" and "booski". He or she is not quite your boyfriend because you are not claiming one another or not ready to claim each other as "boyfriend" or "girlfriend" but you care for each other in a romantic fashion.
If you make out and have dates, you can still be "boojoint" and not "boy/girlfriend".
"I was on AIM last night with my boojoint, we're going to the movies together this afternoon!"
"My boojoint was holding my hand."