- botany the relatively large type of leaf produced by ferns and seed plantsCompare microphyll
- A leaf with several or many large veins branching apart or running parallel and connected by a network of smaller veins. The fronds of ferns and the leaves of gymnosperms and angiosperms are megaphylls. Megaphylls are thought to have evolved from groups of branched stems that have become fused together. Also called macrophyll Compare microphyll.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.