any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response
someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous); "the speaker at commencement"; "an utterer of useful maxims"
the presiding officer of a deliberative assembly; "the leader of the majority party is the Speaker of the House of Representatives"