A watchword; a word or phrase that serves as one's guide.
A word that is printed at the top or bottom of the page in a reference work, in order to help readers find a specific entry.
Any of the words in a memo or email that define metadata regarding the message, such as sender, recipient, and subject.
A sentry, watch, or guard.
A unique string of characters recognised by a computer program for processing in a special way; a keyword.
A sentinel crab.
A sign of a health risk (e.g. a disease, an adverse effect).
To post as guard.
To post a guard for.
To watch over as a guard.