1. A person who is such a massive twat that they more accurately ressemble a big, quivvering sack of twats.
2. A womans pants.
1. 'What's happened Tom? I thought you and Claire were talking again?'
'Well thats right, we were. Until, that was, she unintentionally reminded me of what a complete fucking twatsack she really is.'
2. 'I tell you what Tim, have you got any babywipes? I've been stomping so hard in that sweaty mosh I really should have planned ahead and brought some clean twatsacks with me. They're kicking out right offensive mate.'
Quite simply a womans vagina with a pair of bollocks hanging out of the vagina
hey dude did you fuck that girl you pulled last night?
nah man i went to go down on her but she had a twat sack, so i ran away vomiting!