fortition

1988, Sylvia Moosmüller, Sociophonology, Peter Auer, Aldo di Luzio (editors), Variation and Convergence: Studies in Social Dialectology, page 76, The two process types following from these assumptions, lenition processes, aiming at articulatory ease at the expense of perception, and fortition processes, resulting in articulatory difficulty in favor of better perception, were further modified by Dressler & Drachman (1977), as lenitions need not necessarily impede perception; similarly fortitions need not necessarily result in articulatory difficulty.

2011, Matthew Gordon, 39: Stress: Phonotactic and Phonetic Evidence, Marc van Oostendorp, Colin J. Ewen, Elizabeth V. Hume, Keren Rice (editors), The Blackwell Companion to Phonology, Volume II: Suprasegmental and Prosodic Phonology, page 924, Typically, stressed syllables trigger qualitative fortition and/or lengthening, whereas unstressed syllables are associated with lenition and/or shortening.