Green’s Dictionary of Slang

1. to thrash; thus raasing n., a beating.

1959		A. Salkey Quality of Violence (1978) 111: One shouted: ‘I ready to go for them! Just say the word, Mother! Just say the word!’ The other two shouted: ‘Ready to rass! Ready to rass!’.
1995		Francis-Jackson Official Dancehall Dict. 43: Raasing a thorough thrashing: u. give de bwoy a raasing.
2015		67 ‘It’s Frying’ 🎵 We had sweets in that dotty tray but we rast his ass with the flipping mac.

2. to rush about, to rush away.

1968		A. Salkey Late Emancipation of Jerry Stover (1982) 19: Thieves on all three sides, opportunists on two, and everybody rassing around and aspiring to middle class status.
1973		E. Braithwaite ‘Folkways’ in Arrivants 32: But bes’ leh we get to rass o’ this place; out o’ this ass hole. [...] To rass o’ this work-song.

3. (also rass up) to stir up, to excite.

1968		A. Salkey Late Emancipation of Jerry Stover (1982) 51: The Termites are all small boys, rassed up by the Island and floundering like a bitch.
2018-20		T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Rass up - disrupt, cause confusion.