The Collaborative International Dictionary of English v.0.48:

Synapta \Syn*ap"ta\ (s[i^]n*[a^]p"t[.a]), n. [NL., fr. Gr.
   synapto`s fastened together; sy`n with + 'a`ptein to fasten.]
   (Zool.)
   A genus of slender, transparent holothurians which have
   delicate calcareous anchors attached to the dermal plates.
   See Illustration in Appendix.
   [1913 Webster]