intruder (n.)
- arrival
- arriviste
- blemish
- burglar
- busybody
- buttinsky
- comer
- crasher
- emigrant
- encroacher
- entrant
- gatecrasher
- greenhorn
- immigrant
- impurity
- infiltrator
- interloper
- invader
- kibitzer
- meddler
- misfit
- mote
- newcomer
- oddball
- parvenu
- recruit
- rookie
- settler
- sliver
- snooper
- speck
- splinter
- squatter
- stone
- stowaway
- tenderfoot
- thief
- trespasser
- upstart
- visitant
- visitor
- weed