from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. To take within, as in telescoping one part of the intestine into another; invaginate.
from The Century Dictionary and Cyclopedia
- To take up into itself or into something else; invaginate.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- v. introvert or invaginate
Probably back-formation from intussusception.(American Heritage® Dictionary of the English Language, Fourth Edition)