the GNU version of the Collaborative International Dictionary of English
n. The state or quality of being immature; immaturity.
The Century Dictionary and Cyclopedia
n. Immaturity.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. not having reached maturity
Word Usage
"It is true that for a few years after leaving the cradle he had exhibited a certain immatureness, but as soon as he put on knickerbockers and began to go about a little he outgrew all that."