adjective.
Having the form of threads or filaments; filamented.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adjective.
thin in diameter; resembling a thread
Word Usage
"However, given that H1 is not essential in simple metazoans, such as filamentous fungi and also in specialized protozoa, we have good reason to suspect it might likewise be nonessential for less specialized protozoa."