Devout or pious orthodox Jew.
To be frum (Yiddish: פֿרום; also transliterated frim; meaning “devout” or “pious”) is to be committed to the observance of Jewish religious law in a way that often exceeds the bare requirements of halakha, the collective body of Jewish religious laws. This not only includes the careful study of Torah, daily prayers, observing Shabbat and kashrut, and performing deeds of loving-kindness, but also many more customs and khumrot. Khumrot are prohibitions or obligations in Jewish life that exceed the requirements of Halakha; some khumrot became customs in some communities over time, e. g., daily ritual immersion in a mikveh in Hasidic Judaism or kapparot in Haredi Judaism.
Someone who is frum is known as a frum Jew, a frummer (“pious one”, related to German “ein Frommer”), or frummie (Yinglish diminutive “pious one”). These appellations are generally, but not only, applied to Orthodox Judaism, and used by some members of these groups as a self-reference. To follow a frum path in life implies the constant maintenance of an awareness of God by following spiritual practice as a makhmir, meaning “taking the stricter position on an issue”. In this way, the Ashkenazi frum-culture is variously seen as a precaution against transgressing the Halakha , or as a way of keeping those who have taken on the stringency separate from those who have not.
In Ashkenazi Orthodox communities, the Yinglish initialism “FFB”, meaning “Frum From Birth”, is often used to refer to a person who was born into a religiously observant family and has maintained this lifestyle, in contrast to a “BT”, referring to a baal teshuva.
In the Ashkenazi community, the adjective frei (Yiddish and German “free”) is used as an appellation by Jews with a secular background or by those who adhere to non-Orthodox denominations. A person who calls himself “frei” means one who is less religious and free from the observance of Halakha that exceeds the baseline requirement, or one who is not religiously observant and feels “frei” to do whatever one feels like doing.