im·plead 
(
ĭm-pl
ēd
)
tr.v. im·plead·ed,
im·plead·ing,
im·pleads To sue (a third party) in a lawsuit that has already been commenced as a defendant who may be liable for the claim that is the subject of the suit.
[Middle English empleden, from Anglo-Norman empleder, variant of Old French emplaider : en-, intensive pref. (from Latin in-; see IN-2) + plaidier, to plead; see PLEAD.]