The awkward sound that is sometimes made by a person giving a blow job. This typically happens for one of the following reasons:
1) There is a lot of saliva involved
2) The penis is rather thick and hard to keep one's mouth around
3) The person sucking is trying to avoid using teeth as much as possible
4) The person sucking is inexperienced at giving BJ's
"She rocks at giving head, although she does guggle a lot."