(idiomatic) A quiet, non-participating, or unseen observer; an eavesdropper or witness.

present participle of walk

Incarnate as a human; living. / Able to walk in spite of injury or sickness. / Characterized by or suitable for walking. / Heavily characterized by some given quality.

gerund of walk.

Used other than figuratively or idiomatically: A recreational walk in a park. / (idiomatic) Something easy or pleasant.

(cytology) A thick, fairly rigid, layer formed around individual cells of bacteria, Archaea, fungi, plants, and algae (but not animals and other protists which generally have cell membranes without cell walls). The cell wall is external to the cell membrane and serves a structural function helping the cell maintain its shape and protecting the cell from damage.

(performing arts, idiomatic) The imaginary invisible wall at the front of the stage in a proscenium theatre, through which the audience sees the action in the world of the play.

The acrobatic feat of walking on a tightrope.

(figuratively) To undertake a precarious course of action.

An acrobat who practices tightrope walking.