nonparticipant
noncooperator
nonmember
nonattendee
nonparticipating
nonparticipator
nonresponder
nonpartisan
nonvoter
baulker
balker
noncompliant
neuter
inactive
exile
expatriate
expat
absentee
non partant
off board
unparticipating
nonsharer
uneligible
noneligible
nonsignatory
non-relative
nonattender
nondelegate
opt out
observer
forgoer
nonqualifier
nonadherent
crasher
stayaway
nonjoiner
AWOL
nonsigner
forfeit
nonrecipient
per procurationem
non-responder
ineligible
lookers-on see most of the game
serononresponder
nondriver
nonparticipation
disqualification
unsociable
refusenik