An alderman is someone who has been elected to a municipal council.
Political correctness and anti-sexism has, for the most part, rid us of this problem of mistaking aldermen for men with woodies or vice versa. A few places went the route of using both alderman and alderwoman (a wooden woman because women can’t have woodies?) job titles to reflect the fact that women are now represented in municipal politics, but most towns and cities have done away with the term alderman entirely and replaced it with the term councilor instead. I guess they don’t get erections regardless of which sex they are.