Marasmodes defoliata belongs to a small shrubby genus that is characterized by its ericoid, small, entire to divided and sessile to sub-sessile, linear leaves,and discoid, homogamous flower heads (which means they are made up of just one type of floret, either all ray florets or all disk florets), that are solitary or in groups attached to a flat receptacle, without pits.

Marasmodes defoliata is a small, diffuse shrub 200–400 mm high with thin branched stems that are polygonal to nearly round in cross-section and glabrous.The leaves are linear, 9–23 mm long, sessile, erect-patent, entire, deciduous (caducous), blackish, glandular-punctate, and with short apiculi, and are usually found only on upper branches or branch tips. The capitula (flower head) is discoid, solitary or in groups of up to three, broadly campanulate, 6–10 x 5–7 mm, containing 20–35 (up to 40) phyllaries in 4–5 rows. The inner phyllaries are notable for their purple, scarious tips, 1–2 mm long. There are approximately 20 florets per capitulum, with yellowish corollas featuring sessile glands. The lobes are triangular and recurved. The cypselas (fruits) are oblong, slightly obconical, 1.5–2 mm long, 5-ribbed, and covered with sessile glands. The pappus is composed of 10–12 unequal scarious scales, ranging from 0.2 to 1 mm in length. Flowering time is autumn (April to May).