The American Heritage® Dictionary of the English Language, 4th Edition
n. Any of the proteinaceous cylindrical hollow structures that are distributed throughout the cytoplasm of eukaryotic cells, providing structural support and assisting in cellular locomotion and transport.
n. small tubes made of protein and found in cells; part of the cytoskeleton.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a microscopically small tubule
Word Usage
"The common view was that microtubules all began at the cell body; the graph should have simply shown a decrease in microtubule number as one looked further from the cell body."