Used in a phrase to express dislike for a situation or place.
It can refer to the bad effects of drugs, alcohol, boredom, work, sport etc.
'Man, I'm on a whitey after last night''
'If the scousers win tomorrow it'll send me on a whitey'
Often used in a phrase to suggest that something is bad or unfavourable.
'this hangover is sending me west'
'don't go to *insert shitty town here* it will send you west'