Synonyms for Opening:

adj.

beginning (adjective)
initiatory, initial.
earliest (adjective)
original.

n.

blowhole, crater, cavity, channel, abyss, chink, primary, cleft, cranny. early, new, from the get-go, all along, outlet, vent, original, front end, initial, open, at first. onset, conception, nascency, arrival, appearance, genesis, dawn, starting point, nascence, birth. appointment, delegation, call, kickoff, career, incipiency, collaboration, origination, leadoff, launch, business, background, division of labor, incipience, calling. window of opportunity, occasion, Possibilities, choice, chance, scope, opportunity, the initiative, shot, luck. burst open, try, unscrew, open up, force, unfold, undo, crack something open, unlock, pry. beginning (noun)
dawn, starting point, incipience, incipiency, birth, kickoff, leadoff, launch, onset.
chance (noun)
occasion, shot, scope, opportunity, possibility.
entrance (noun)
aperture, intake, entrance, ingress, input, access, entryway, door.
gap, hole (noun)
chink, cavity, vent, mouth, door, scuttle, cleft, aperture, outlet, cranny, orifice, hatch.
introduction (noun)
introduction, overture, preface, preamble, prelude, prologue, forward.
object (noun)
gap.
opening (noun)
first step, inlet, embouchure, gate, pore, chasm, hatch, first, introductory, maiden, curtain raising, initiatory, hatchway, gap, mouth, porta, starting, orifice, inaugural, beginning, scuttle, yawning, portal, possibility, opening night, possible action, initiative, opening move.
premiere (noun)
opening night.

v.

opening (verb)
unplugging, revealing, unlocking, disclosing, baring, Exposing, undoing, unsealing, uncorking, releasing.

Other synonyms:

genesis, nascence, window of opportunity, all along, origination, leadoff, opportunity, incipience, incipiency, nascency, front end. new, occasion, onset, kickoff. original, outlet, scope, dawn. shot, choice. vent, early. chance, birth. Other relevant words:
calling, open, business, abyss, initiative, introductory, starting, vent, chance, porta, inaugural, force, original, background, appearance, new, dawn, try, cranny, crater, conception, Possibilities, scuttle, occasion, window of opportunity, incipience, collaboration, front end, hatchway, origination, outlet, maiden, scope, unscrew, early, initiatory, arrival, nascence, first, appointment, open up, primary, channel, starting point, leadoff, luck, onset, shot, possible action, cleft, delegation, kickoff, curtain raising, unlock, choice, cavity, undo, pry, opportunity, unfold, initial, beginning, possibility, launch, genesis, opening night, blowhole, access, birth, call, nascency, incipiency, chink, opening move, career, first step.

Usage examples for opening

  1. John Sammons asked, his eyes opening wide in surprise. – The Minute Boys of the Mohawk Valley by James Otis
  2. Off with you through that opening – A Dash from Diamond City by George Manville Fenn