by·word also by-word 
(bīwûrd′)
(bīwûrd′)n.
1.
a. A proverbial expression; a proverb.
b. An often-used word or phrase.
2. One that represents a type, class, or quality: "Polyester got its déclassé reputation in the 1970s after cheap, poorly made double-knit leisure suits became a byword for bad taste" (Fortune).
3. An object of notoriety or interest: The eccentric poet was a byword in literary circles.
4. An epithet.
[Middle English byworde, from Old English bīword, translation of Latin prōverbium.]