1.  tracing(n = noun.act) - the act of drawing a plan or diagram or outline;
Derived form verb trace₂

2.  tracing(n = noun.artifact) trace - a drawing created by superimposing a semitransparent sheet of paper on the original image and copying on it the lines of the original image;

3.  tracing(n = noun.act) - the discovery and description of the course of development of something; "the tracing of genealogies"

1.  The act of one who traces; especially, the act of copying by marking on thin paper, or other transparent substance, the lines of a pattern placed beneath; also, the copy thus producted. [1913 Webster]

2.  A regular path or track; a course. [1913 Webster]

tracing, n.
1 a copy of a drawing etc. made by tracing.
2 = TRACE(1) n. 3.
3 the act or an instance of tracing.

Idiom:
tracing-paper translucent paper used for making tracings.

N  copy, facsimile, counterpart, effigies, effigy, form, likeness, image, picture, photo, xerox, similitude, semblance, ectype, photo offset, electrotype, imitation, model, representation, adumbration, study, portrait, resemblance, duplicate, reproduction, cast, tracing, reflex, reflexion, reflection, shadow, echo, transcript, transcription, recording, scan, chip off the old block, reprint, new printing, rechauffe, apograph, fair copy, parody, caricature, burlesque, travesty, travestie, paraphrase, derivative, derivation, modification, expansion, extension, revision, second edition, servile copy, servile imitation, plagiarism, counterfeit, fake, pasticcio, faithful, lifelike, close, conscientious, unoriginal, imitative, derivative.

N  representation, representment, imitation, illustration, delineation, depictment, imagery, portraiture, iconography, design, designing, art, fine arts, painting, sculpture, engraving, photography, cinematography, radiography, autoradiography, fluorography, sciagraphy, personation, personification, impersonation, drama, picture, photo, photograph, daguerreotype, snapshot, X-ray photo, movie film, movie, tracing, scan, TV image, video image, image file, graphics, computer graphics, televideo, closed-circuit TV, copy, drawing, sketch, drought, draft, plot, chart, figure, scheme, image, likeness, icon, portrait, striking likeness, speaking likeness, very image, effigy, facsimile, figure, figure head, puppet, doll, figurine, aglet, manikin, lay- figure, model, mammet, marionette, fantoccini, waxwork, bust, statue, statuette, ideograph, hieroglyphic, anaglyph, kanji, diagram, monogram, map, plan, chart, ground plan, projection, elevation (plan), ichnography, cartography, atlas, outline, scheme, view, radiograph, scotograph, sciagraph, spectrogram, heliogram, represent, representing, representative, illustrative, represented, imitative, figurative, iconic, like, graphic, cinquecento quattrocento, trecento.