Simply sexual boasting. Most frequently seen in young people who are having their first sexual experiences.
                                                            
                                                     
                        
                                                
                        
                        
                            an instance of boastful talk; "his brag is worse than his fight"; "whenever he won we were exposed to his gasconade" 
                                                            
                                                     
                        
                                                
                        
                        
                            exhibiting self-importance; "big talk"