Which word describes an idea or meaning associated with a word or thing?

The term that accurately describes an idea or meaning associated with a word or thing is connotation. Connotation refers to the emotional or cultural associations that a word may invoke in addition to its literal meaning. For example, the word "home" carries connotations of warmth, safety, and comfort, which extend beyond its basic definition as a physical dwelling.

In contrast, the other options do not relate to the idea of associated meanings. Corroborate pertains to confirming or strengthening an argument with evidence, countenance relates to a person's facial expression or demeanor, and concatenate means to link things together in a series or chain. None of these terms convey the nuance of meaning inherent in the connotation of a word.