Synonyms for Sentinel

°A sentry or guard.

°a unique string of characters recognised by a computer program for processing in a special way; a keyword.

°To watch over as a guard.

°To post as guard.

(n) : a sentry or guard; a unique phrase of characters (a string), used to mark a document for processing by a computer program, also called a keyword. For example, an HTML tag such as '<table>' is a form of sentinel as its a unique phrase that is non-reaccuring in the english language. However the use of '<' and 'table' do occur in english but not in this form, so '<table>' is a relatively good sentinel phrase

(v) : to watch over something as a guard