1. subst. A common substance, chemically consisting mainly of sodium chloride (NaCl), used extensively as a condiment and preservative.
2. subst. (chemistry) One of the compounds formed from the reaction of an acid with a base, where a positive ion replaces a hydrogen of the acid.
3. subst. (uncommon) A salt marsh, a saline marsh at the shore of a sea.
4. subst. (slang) A sailor (also old salt).
5. subst. (cryptography) Randomly chosen bytes added to a plaintext message prior to encrypting or hashing it, in order to render brute-force decryption more difficult.
6. subst. A person who seeks employment at a company in order to (once employed by it) help unionize it.
7. subst. (obsolete) Flavour; taste; seasoning.
8. subst. (obsolete) Piquancy; wit; sense.
Attic salt
9. subst. (obsolete) A dish for salt at table; a salt cellar.
10. subst. (figurative) Skepticism and common sense.
Any politician's statements must be taken with a grain of salt, but his need to be taken with a whole shaker of salt.