The Collaborative International Dictionary of English v.0.48:

Liquid \Liq"uid\ (l[i^]k"w[i^]d), a. [L. liquidus, fr. liquere
   to be fluid or liquid; cf. Skr. r[imac] to ooze, drop,
   l[imac] to melt.]
   1. Flowing freely like water; fluid; not solid.
      [1913 Webster]

            Yea, though he go upon the plane and liquid water
            which will receive no step.           --Tyndale.
      [1913 Webster]

   2. (Physics) Being in such a state that the component
      molecules move freely among themselves, but have a
      definite volume changing only slightly with changes of
      pressure, and do not tend to separate from each other as
      the particles of gases and vapors do when the volume of
      the container is increased; neither solid nor gaseous; as,
      liquid mercury, in distinction from mercury solidified or
      in a state of vapor.

   Note: Liquid substances may form a definite interface with
         gases, whereas the molecules of different gases freely
         intermingle with each other.
         [1913 Webster +PJC ]

   3. Flowing or sounding smoothly or without abrupt transitions
      or harsh tones. "Liquid melody." --Crashaw.
      [1913 Webster]

   4. Pronounced without any jar or harshness; smooth; as, l and
      r are liquid letters.
      [1913 Webster]

   5. Fluid and transparent; as, the liquid air.
      [1913 Webster]

   6. Clear; definite in terms or amount. [Obs.] "Though the
      debt should be entirely liquid." --Ayliffe.

   7. (Finance) In cash or readily convertible into cash without
      loss of principle; -- said of assets, such as bank
      accounts, or short-term bonds tradable on a major stock
      exchange.
      [PJC]

   Liquid glass. See Soluble glass, under Glass.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Liquid \Liq"uid\, n.
   1. A substance whose parts change their relative position on
      the slightest pressure, and therefore retain no definite
      form; any substance in the state of liquidity; a fluid
      that is not gaseous and has a definite volume independent,
      of the container in which it is held. Liquids have a fixed
      volume at any given pressure, but their shape is
      determined by the container in which it is contained.
      Liquids, in contrast to gases, cannot expand indefinitely
      to fill an expanding container, and are only slightly
      compressible by application of pressure.
      [1913 Webster]

   Note: Liquid and fluid are terms often used synonymously, but
         fluid has the broader signification. All liquids are
         fluids, but many fluids, as air and the gases, are not
         liquids.
         [1913 Webster]

   2. (Phon.) A letter which has a smooth, flowing sound, or
      which flows smoothly after a mute; as, l and r, in bla,
      bra. M and n also are called liquids.
      [1913 Webster]

   Liquid measure, a measure, or system of measuring, for
      liquids, by the gallon, quart, pint, gill, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

liquid
    adj 1: existing as or having characteristics of a liquid;
           especially tending to flow; "water and milk and blood are
           liquid substances" [ant: gaseous, solid]
    2: filled or brimming with tears; "swimming eyes"; "sorrow made
       the eyes of many grow liquid" [syn: liquid, swimming]
    3: clear and bright; "the liquid air of a spring morning"; "eyes
       shining with a liquid luster"; "limpid blue eyes" [syn:
       liquid, limpid]
    4: changed from a solid to a liquid state; "rivers filled to
       overflowing by melted snow" [syn: melted, liquid,
       liquified] [ant: unmelted]
    5: smooth and flowing in quality; entirely free of harshness;
       "the liquid song of a robin"
    6: smooth and unconstrained in movement; "a long, smooth
       stride"; "the fluid motion of a cat"; "the liquid grace of a
       ballerina" [syn: fluent, fluid, liquid, smooth]
    7: in cash or easily convertible to cash; "liquid (or fluid)
       assets" [syn: fluid, liquid]
    n 1: a substance that is liquid at room temperature and pressure
    2: the state in which a substance exhibits a characteristic
       readiness to flow with little or no tendency to disperse and
       relatively high incompressibility [syn: liquid,
       liquidness, liquidity, liquid state]
    3: fluid matter having no fixed shape but a fixed volume
    4: a frictionless continuant that is not a nasal consonant
       (especially `l' and `r')

Moby Thesaurus II by Grady Ward, 1.0:

199 Moby Thesaurus words for "liquid":
   accented, alcoholic drink, allophone, alveolar, apical,
   apico-alveolar, apico-dental, aquatic, aqueous, articulated,
   articulation, aspiration, assimilated, assimilation, back,
   barytone, beverage, bilabial, blood, bright, brilliant, broad,
   cacuminal, central, cerebral, check, checked, clear, close,
   consonant, consonantal, continuant, convertible, dental, diphthong,
   dissimilated, dissimilation, dorsal, drink, drinkable,
   epenthetic vowel, explosive, flat, flowing, fluent, fluid,
   fluid extract, fluid mechanics, fluidal, fluidic, fluxible,
   fluxile, fluxional, fluxionary, front, frosted, frosted shake,
   glide, glossal, glottal, glottalization, golden, guttural, hard,
   heavy, high, honeyed, hydrated, hydraulic, hydraulics,
   hydrogeology, hydrous, intonated, juice, juicy, labial,
   labialization, labiodental, labiovelar, laryngeal, lateral, latex,
   lax, light, limpid, lingual, liquefied, liquid extract, liquidy,
   liquor, low, malt, manner of articulation, mellifluent, mellow,
   melted, mid, milk, modification, molten, monophthong,
   monophthongal, morphophoneme, mute, muted, narrow, nasal,
   nasalized, negotiable, occlusive, open, oxytone, palatal,
   palatalized, parasitic vowel, peak, pharyngeal, pharyngealization,
   pharyngealized, phone, phoneme, phonemic, phonetic, phonic, pitch,
   pitched, plashy, plosive, pop, posttonic, potable, potation,
   profitable, prothetic vowel, retroflex, rounded, running, runny,
   sap, sappy, segmental phoneme, semiliquid, semivowel, shake,
   shining, sloppy, soda, soda pop, soda water, soft, soft drink,
   solution, solvent, sonant, sonority, speech sound, splashy, stop,
   stopped, stressed, strong, succulent, surd, swashy, syllabic,
   syllabic nucleus, syllabic peak, syllable, tense, thick, throaty,
   tonal, tonic, transition sound, translucent, transparent,
   triphthong, twangy, unaccented, unrounded, unstressed, velar,
   vocable, vocalic, vocoid, voice, voiced, voiced sound, voiceless,
   voiceless sound, voicing, vowel, vowellike, water, waterish,
   watery, weak, whey, wide