The term 'vocative' is a grammatical case used in some languages to indicate the person or thing being addressed. The crossword solution for vocative is 'GLIB', which means 'fluent and voluble in speech, often in a way that is thought to be insincere or superficial'. Therefore, the term 'GLIB' can be used to describe someone who speaks in a way that is thought to be insincere or superficial when addressing someone else.