D defs.my
Entry 2 senses Webster, 1913

Watchword

/wäch'-wẽrdˌ/ · Watch·word · IPA /ˈwɒt͡ʃwɜː(ɹ)d/
01 n. A word given to sentinels, and to such as have occasion to visit the guards, used as a signal by which a friend is known from an enemy, or …
  1. 1.
    A word given to sentinels, and to such as have occasion to visit the guards, used as a signal by which a friend is known from an enemy, or a person who has a right to pass the watch from one who has not; a countersign; a password.
  2. 2.
    A sentiment or motto; esp., one used as a rallying cry or a signal for action.
    “Nor deal in watchwords overmuch.” Tennyson.