Definition of "subtitle"

Careful viewers have long observed that in the movies, one can not only watch but read cigarettes like subtitles — translating the action on the screen into another language which the camera registers but rarely foregrounds, a part of the thickness of the medium which is almost never brought into focus. […] The cigarette in the scene serves as a subtext, a mute caption or subtitle, sometimes accompanying, sometimes contradicting or diverting the explicit premise of the action or the open meaning of signs.

1995, Richard Klein, “Introduction”, in Cigarettes are sublime, Paperback edition, Durham: Duke University Press, published 1993, page 9