mason wasp

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various solitary vespid wasps, especially of the subfamily Eumeninae, that build nests of mud.

from The Century Dictionary.

• noun An aculeate hymenopterous insect of the genus Odynerus, family Vespidæ; a kind of solitary wasp: so called from the ingenuity with which it constructs its habitations in the sand, in the plaster of walls, etc. O. murarius is an example.

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

• noun A potter wasp.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun solitary wasp that constructs nests of hardened mud or clay for the young
• noun any of various solitary wasps that construct nests of hardened mud for their young