| Noun | 1. | underclass - the social class lowest in the social hierarchy social class, socio-economic class, stratum, class - people having the same social, economic, or educational status; "the working class"; "an emerging professional class" |
| Adj. | 1. | underclass - belonging to the lowest and least privileged social stratum; "underclass mothers and children"underprivileged - lacking the rights and advantages of other members of society |