A fungal parasite, such as certain dermatophytes, forming a sheath of spores on the outside of a hair as well as growing within the hair shaft.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Examples from the Web for ectothrix

Historical Examples of ectothrix