Not vague
No. It is a figure of speech. A euphemism is a word substituted for another word that is deemed unacceptably explicit. For example, the word mortician came into vogue as a euphemism for "undertaker," which was considered too direct and to the point.
Yes
a spaceship
A descriptive word or phrase added to or substituted for a person's name is called a nickname. It is often used to reflect a specific characteristic, personality trait, or quality of the individual. Nicknames can be endearing, humorous, or symbolic in nature.
The word knowledgeable could be used to replace the phrase "in the know".
euphanism
Euphemisms are more sensitive word substitutions.
A euphemism is a mild or indirect word or expression substituted for one considered to be too harsh or blunt when referring to something unpleasant or embarrassing. A figure of speech is a word or phrase used in a non-literal or imaginative way for rhetorical effect.
'Explicit' is a Latin word meaning 'he, she, or it explains'.
The word explicit is often used in the sense of sexually explicit.
"Smut" can be considered a vulgar or derogatory term when used to describe explicit or pornographic material. It is often used in a negative context to refer to sexually explicit content.
A euphemism is basically an unoffensive, mild word or phrase substituted for a blunt, harsh word or phrase. For example, instead of saying someone died saying they "passed away," or calling a prison a "correctional facility."