To rob or steal quickly in an inner city- usually accompanied by an unnecessary beating. The act of drapsing someone can be a planned ambush attack or an opportunistic hit.
My man Neil had his phone snatched when he was out walking and gave chase (with the help of a supposedly helpful passer-by, who said he knew of the offender). The chase led into a wooded area of a park...but when they caught up with thief, the sitution turned poor for my man as the "helpful" passer-by turned on him. Others poorly emerged from nearby bushes and proceeded to drapes my man of funds and his watch whilst administating a needless beating.
The act of not coming through on a promising flex (shag).
The phrase originates from Matt going back to Blackpool Jackie's place after a hook up in Rumours. Despite numerous attempts to get past the heavy petting stage- access was continally denied and Matt was left to lie awake in a state of flex limbo until 8 next morning, when he received a plate of cheese on toast for all his hard efforts.
It must have been a particularly good meal as he returned the following 2 nights and received nothing but more cheese on toast.