The Collaborative International Dictionary of English v.0.48:

Logotype \Log"o*type\, n. [Gr. lo`gos word + -type.] (Print.)
   A single type, containing two or more letters; as, [ae],
   \[oe], [AE], [filig], [fllig], [ffllig], etc.; -- called also
   ligature.
   [1913 Webster]

WordNet (r) 3.0 (2006):

logotype
    n 1: a company emblem or device [syn: logo, logotype]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "logotype":
   allegory, ascender, back, bastard type, beard, belly, bevel,
   billhead, black letter, body, book stamp, bookplate, brand,
   broad arrow, cachet, cap, capital, case, charactery, check, cipher,
   colophon, conventional symbol, counter, counterfoil, countermark,
   descender, docket, em, emblem, en, face, fat-faced type, feet,
   font, government mark, government stamp, groove, hallmark,
   iconology, ideogram, imprint, italic, label, letter, letterhead,
   ligature, logo, logogram, love knot, lower case, majuscule,
   masthead, minuscule, nick, pi, pica, pictogram, plate, point,
   price tag, print, registered trademark, roman, running head,
   running title, sans serif, script, seal, shank, shoulder, sigil,
   signet, small cap, small capital, stamp, stem, sticker, stub,
   symbol, symbolic system, symbolism, symbolization, symbology, tag,
   tally, ticket, title page, token, totem, totem pole, trade name,
   trademark, trademark name, type, type body, type class, type lice,
   typecase, typeface, typefounders, typefoundry, upper case