We do not currently know of any antonyms for blanket term.
The noun blanket term is defined as:
A word or phrase that is used to describe multiple groups of related things. The degree of relation may vary. Blanket terms often trade specificity for ease-of-use; in other words, a blanket term by itself gives little detail about the things that it describes or the relationships between them, but is easy to say and remember. Blanket terms often originate as slang, and eventually become integrated into the general vocabulary.
