The American Heritage® Dictionary of the English Language, 4th Edition
adj. Having little or no importance; not essential.
adj. Biochemistry Being a substance that is required for normal functioning but does not need to be included in the diet because of the body's ability to synthesize it from other nutrients.
the GNU version of the Collaborative International Dictionary of English
adj. Not essential.
n. A thing not essential.
The Century Dictionary and Cyclopedia
Not essential or necessary; not absolutely necessary.
n. A thing that is not essential, absolutely necessary, or of the utmost consequence.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. anything that is not essential
adj. not of prime or central importance
Word Usage
"I think all of the above, in a sense, and I liken it to other what I call nonessential passions that we have--golf, for example, horseback riding, neither of which are to my taste."