Sex that keeps you in bed for an extended period of time, only getting up to get food or go to the bathroom.
"Where you been the past few days, man?"
"I was on bed arrest with this amazing hottie I met at a club last weekend!"
Method of detaining people by smashing their door down in the middle of night, piling upstairs and rudely waking them up by screaming/bright lights: they are then led away in handcuffs (if lucky, some victims are simply shot in bed.) Employed by British police forces.
'What the hell happened to your house?'
'I was bed arrested last night, but they actually wanted the guy next door'