Definition of "harbinger"

Make all our Trumpets ſpeak, giue thẽ all breath / Thoſe clamorous Harbingers of Blood, & Death

c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act V, scene vi], page 150, column 2

I knew by these harbingers who were coming.

1828, Walter Savage Landor, Imaginary Conversations, Lord Brooke and Sir Philip Sidney

It’s to realize that Moon Frye, by cheerfully surveilling her own life, and those first Real Worlders, by agreeing to the constant presence of producers and cameras, were the harbingers of today’s culture, in which self-image is shaped in the expectation of a lens and personhood collates with brand identity.

2021 March 26, Alexis Soloski, “‘Kid 90’ and the Days When Even Wild TV Teens Had Privacy”, in The New York Times‎

outward decency […] is the Harbinger to provide the lodging for inward holinesse

1644, Thomas Fuller, Truth Maintained (a sermon)

It was harbingered also by the terrible comet of January, which appeared in a cadent and obscure house, denoting sickness and death; […]

1841, William Harrison Ainsworth, chapter VIII, in Old Saint Paul's, published 1903, page 94