IPA: //ˌsæŋk.tɪˈmoʊ.ni.əs//
KK: /sæŋk.tɪˈmoʊ.ni.əs/
Pretending to be morally better or more religious than others, often in a way that is insincere or hypocritical.
His sanctimonious attitude made it hard for others to take him seriously.
Sanctimonious is formed from "sanctus" (meaning holy) and "-monious" (derived from "monere", meaning to warn or advise). The word describes someone who makes a show of being morally superior or pious, often in a hypocritical manner.
Think of someone who is 'holy' ('sanctus') and 'advising' others on morality ('monere') — this helps you remember that sanctimonious refers to someone who pretends to be morally superior.