the GNU version of the Collaborative International Dictionary of English
n. A feeler; especially, one of the jointed sense organs attached to the mouth organs of insects, arachnids, crustaceans, and annelids. The palpi of male spiders serve as sexual organs. Called also palp. See Illust. of arthrogastra and orthoptera.
The Century Dictionary and Cyclopedia
n. In zoology: One of the jointed organs attached to the labium and maxillæ of insects; a feeler.
n. One of the fleshy lobes at the sides of the mouth of acephalous mollusks. More fully called labial palpus. See second cut under Lamellibranchiata.
Word Usage
"The head has two compound eyes, an antennae to sense chemicals and the mouth parts called the palpus and proboscis."