rough breathing

WordReference Random House Unabridged Dictionary of American English © 2026

rough′ breath′ing, 

1. Linguistics the symbol (‘) used in the writing of Greek to indicate aspiration of the initial vowel or of the ρ (rho) over which it is placed.
2. Linguistics, Phonetics the aspirated sound indicated by this mark. Cf. smooth breathing. 
• translation of Latin spiritus asper 1740–50

Collins Concise English Dictionary © HarperCollins Publishers::

rough breathing noun

1. (in Greek) the sign () placed over an initial letter, or a second letter if the word begins with a diphthong, indicating that (in ancient Greek) it was pronounced with an h
   Compare smooth breathing