offender
sinner
entrant
persona non grata
unwelcome person
alien
boarder
crasher
encroacher
gatecrasher
infiltrator
invader
penetrator
prowler
pusher
sneak
squatter
stalker
stranger
thruster
unknown
unwelcome guest
above
backslider
blusterer
calumniation
cuddle
detainment
disturber
encumbrance
illegality
impenitency
interloper
lawbreakers
mix-up
peculator
ploughboy
self-injury
shedder
stunting
transgressor