After using Google search, this is what I found:
/dɛns/
adjective
closely compacted in substance.
"as the storm cleared, a dense fog came down" synonyms: thick, heavy, opaque, soupy, murky, smoggy, impenetrable; More
informal (of a person) stupid.
"Am I being dense? I don't quite understand"
Definition (1) clearly states that 'dense' is synonymous with 'thick'.
Many words have multiple meanings/definitions. It is context that makes "everything" clear.
If we are eating pancakes and we pour some honey and say that honey is dense, that cannot mean that honey is 'stupid'. (because in the context that we have, honey is a substance, and definition (2) doesn't apply)