exarticulate

from The Century Dictionary.

• To disjoint; put out of joint; luxate.
• In surgery, to sever the ligamentous connections of at a joint; amputate at a joint: as, to exarticulate the thumb.
• In zoology, not jointed; not consisting of two or more joints; inarticulate; composed of a single joint, as the antennæ or palpi of certain insects.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Zoöl.) Having but one joint; -- said of certain insects.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective zoology Having only one joint; said of certain insects.