noun

• (publishing) A written composition of moderate length, exploring a particular issue or subject.
  "In his first book since the 2008 essay collection Natural Acts: A Sidelong View of Science and Nature, David Quammen looks at the natural world from yet another angle: the search for the next human pandemic, what epidemiologists call “the next big one.”"
• (obsolete) A test, experiment; an assay.
• (now rare) An attempt.
  "My first essay at getting employment was fruitless; but after no small number of mortifying rebuffs from various parties to whom I applied for assistance, I was at last rewarded by a comparative success."
• (philately, finance) A proposed design for a postage stamp or a banknote.

verb

• (dated, transitive) To attempt or try.
  "Shall we essay a walk on the promenade?"
• (intransitive) To move forth, as into battle.