Specimens of B. diffracta are quickly identified by their large size and strongly plicate leaves with lamina reflexed above a differentiated, ± sheathing base. The plications are so pronounced that the lamina is wavy in cross-section. The other southern African species of Breutelia have only weak plications that are restricted to the leaf base.
Plants medium-sized to large, frequently robust, forming large, loose cushions, yellowish green, brownish below; terricolous or saxicolous. Stems 50-150(-200) mm tall, irregularly branched, generally with dense reddish brown tomentum on lower stem; in section elliptical, central strand present, small, inner cortical cells in 8-12 rows, thin-walled, smaller and more strongly thickened toward outside, outer cortical cells in 2-3 rows, stereids, reddish, epidermal cells thin-walled, fragile, outer wall quickly broken away resulting in fluted stem. Leaves ± distant, lamina widespreading to squarrose above erect, sheathing base, weakly contorted dry, strongly plicate from base to upper leaf; long-acuminate above short- obovate base, 3.0-4.0(-4.5) mm long, 1.0-1.5 mm wide at shoulders; lamina occasionally with small bistratose patches not associated with plications; margins plane, serrate to strongly serrate above base, occasionally with double teeth. Costa short-excurrent, serrate, superficial cells rectangular, smooth, incrassate; in section elliptical, guide cells large, incrassate, ventral stereid band 1-2(-3) cells thick, exposed, occasionally substereids, dorsal stereid band 3-4 cells thick, occasionally substereids, dorsal surface cells undifferentiated or frequently substereids. Laminal cells rectangular, weakly thickened, ends rounded, 5-7:1, cells rarely strongly thickened, cells prorate at proximal ends, or occasionally with single papillae at proximal end; inner basal cells moderately differentiated, rectangular, 10:1, strongly thickened at insertion; alar and lower marginal cells distinct, broad and lax. Dioicous. Perichaetia lateral through innovation. Seta 10-15 mm long, red-yellow; capsule inclined, urn globose to ovoid wet, urceolate and striated dry, 3-4 mm long; exothecial cells quadrate to hexagonal, weakly thickened, yellowish, 6 rows at mouth transversely rectangular, reddish; stomata not seen; peristome absent; operculum convex; calyptra not seen; spores subround, 30-40 µm, surface with irregular wartlike plates, red-brown.