NOUN (4)

1. (anatomy) a somewhat rounded subdivision of a bodily organ or part;
- Example: "ear lobe"

2. (botany) a part into which a leaf is divided;

3. the enhanced response of an antenna in a given direction as indicated by a loop in its radiation pattern;

4. a rounded projection that is part of a larger structure;

The Collaborative International Dictionary of English v.0.48:

Lobe \Lobe\ (l[=o]b), n. [F. lobe, Gr. lobo`s.]
   Any projection or division, especially one of a somewhat
   rounded form; as:
   (a) (Bot.) A rounded projection or division of a leaf.
       --Gray.
   (b) (Zool.) A membranous flap on the sides of the toes of
       certain birds, as the coot.
   (c) (Anat.) A round projecting part of an organ, as of the
       liver, lungs, brain, etc. See Illust. of Brain.
   (b) (Mach.) The projecting part of a cam wheel or of a
       non-circular gear wheel.
       [1913 Webster]

   Lobe of the ear, the soft, fleshy prominence in which the
      human ear terminates below, also called the earlobe.
      See. Illust. of Ear.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

lobe
    n 1: (anatomy) a somewhat rounded subdivision of a bodily organ
         or part; "ear lobe"
    2: (botany) a part into which a leaf is divided
    3: the enhanced response of an antenna in a given direction as
       indicated by a loop in its radiation pattern
    4: a rounded projection that is part of a larger structure

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "lobe":
   Eustachian tube, anvil, appendage, arachnoid, arbor vitae,
   archipallium, arm, auditory apparatus, auditory canal,
   auditory meatus, auditory nerve, auditory ossicles, auditory tube,
   auricle, basilar membrane, between brain, bony labyrinth, bough,
   brain stem, branch, cauliflower ear, cerebellar hemispheres,
   cerebellum, cerebral cortex, cerebrospinal fluid, cerebrum,
   cochlea, conch, concha, convolution, corpus callosum,
   corpus striatum, diencephalon, drape, drumhead, dura mater, ear,
   ear lobe, eardrum, endbrain, endolymph, external ear, fissure,
   folia, forebrain, fornix, frontal lobe, glial cells,
   globus pallidus, gray matter, gyrus, hammer, hand, hanger, hanging,
   hindbrain, hippocampus, hypothalamus, imp, incus, inner ear, joint,
   lappet, leg, lenticular nucleus, limb, limbic lobe, link,
   little brain, lobation, lobule, lug, malleus, mantle,
   mastoid process, medulla oblongata, member, meninges,
   mesencephalon, metencephalon, midbrain, middle ear, myelencephalon,
   neopallium, occipital lobe, offshoot, optic chiasm, organ,
   organ of Corti, outer ear, oval window, pallium, parietal lobe,
   pendant, perilymph, pia mater, pineal body, pinion, pinna,
   pituitary body, pons, ramification, reticular system,
   rhombencephalon, round window, runner, scion, secondary eardrum,
   semicircular canals, shell, spray, sprig, spur, stapes, stirrup,
   subthalamus, switch, tail, telencephalon, temporal lobe, tendril,
   thalamus, twig, tympanic cavity, tympanic membrane, tympanum,
   uvula, ventricle, vermis, vestibule, white matter, wing