IPA: //ˈtʃeɪstər//
KK: /ˈtʃeɪstər/
More pure or modest than others; having a higher standard of sexual morality.
She is considered chaster than her peers due to her strict values.
Comparative: chaster
Superlative: chastest
Chaster is derived from the word "chaste" (from Latin "castus", meaning pure or unblemished) and the suffix "-er" (meaning one who). The term "chaster" refers to one who is more chaste or pure than another.
Think of someone who is 'more pure' ('chaste') — the '-er' indicates that they are one who possesses that quality to a greater degree.