What familiar English word contains the three letters XOP in that order and all in a row?

Most common Word probably is saxophone. Here are others:

8-letter Words

axoplasm

9-letter Words

axoplasms, Saxophone, toxophily

10-letter Words

axoplasmic, saxophones, saxophonic, toxoplasma

11-letter Words

saxophonist, toxophilies, toxophilite, toxoplasmas, toxoplasmic

12-letter Words

exopeptidase, exophthalmic, exophthalmos, exophthalmus, saxophonists, toxophilites

13-letter Words

exopeptidases, toxoplasmoses, toxoplasmosis

14-letter Words

exophthalmoses, exophthalmuses