A derogatory name for a snivelling, pathetic male. A sleazy creep who thinks he is a massive stud and can have any woman he wants when actually they are all wishing he would just f**k off. He needs to man up and get on with his life.
For a more detailed description please see Jude Law in the movie 'Closer'.
"He is such an unbelievable Batweasel, he needs to grow some balls and behave more like Clive Owen'