noun

• (uncountable, archaic) Verbal exchange, conversation.
  "UUho when he ſhal embrace you in his arms UUil tell how many thouſand men he ſlew. And when you looke for amorous diſcourſe, Will rattle foorth his facts of war and blood: […]"
• (uncountable) Expression in words, either speech or writing.
  "Drawings and pictures are more than mere ornaments in scientific discourse. Blackboard sketches, geological maps, diagrams of molecular structure, astronomical photographs, MRI images, the many varieties of statistical charts and graphs: These pictorial devices are indispensable tools for presenting evidence, for explaining a theory, for telling a story."
• (countable) A conversation.
  "It ſeems, the Minds of theſe People are ſo taken up with intenſe Speculations, that they neither can ſpeak, nor attend to the Diſcourſes of others, without being rouzed by ſome external Taction upon the Organs of Speech and Hearing; for which reaſon, thoſe Perſons who are able to afford it always keep a Flapper (the Original is Climenole) in their Family, as one of their Domeſticks, nor ever walk abroad or make Viſits without him."
• (countable) A formal lengthy exposition of some subject, either spoken or written.
  "The preacher gave us a long discourse on duty."

verb

• (intransitive) To engage in discussion or conversation; to converse.
• (intransitive) To write or speak formally and at length.
• (obsolete, transitive) To debate.
• (obsolete, transitive) To produce or emit (musical sounds).
  "Hamlet. […] Will you play upon this pipe? […] It is as easy as lying. Govern these ventages with your fingers and thumbs, give it breath with your mouth, and it will discourse most eloquent music."