IPA: /ˈtiːˌtoʊlər/
KK: /ˈtiːˌtoʊlər/
A person who does not drink any alcoholic drinks at all.
As a teetotaler, she always chooses non-alcoholic beverages at parties.
Teetotaler is formed from "tee" (a reduplication of the first syllable of "total") and "total" (from Latin "totus", meaning whole or entire). The term originally referred to someone who completely abstains from alcohol, emphasizing total abstinence.
Think of someone who is 'totally' ('total') committed to not drinking alcohol — that's what a teetotaler means.