Crinum lugardiae is a deciduous, summer-growing bulbous plant, 280–350 mm tall. The bulb is globose, 40–70 mm in diameter, single, with a distinct neck 40–120 mm long, clothed in many layers of dark brown, cartilaginous outer tunics. The leaves are arranged in a rosette, and are narrowly strap-shaped, measuring 290–400 mm in length and 8–30 mm in width. They are spreading or arching, leathery, deeply channelled, bright green or greyish-green (glaucous) and they occur at the same time as the flowers. The margins are flat or mildly to moderately undulate, ciliate and narrowly cartilaginous.

The inflorescence is an umbel of eight to thirteen flowers, the peduncle is erect to suberect, slender, 150–300 mm in length; the spathe bracts are lanceolate, spreading and measure 45-110 mm in length by 10–25 mm in width. The pedicels are light green, erect and vary in length from 5–20 mm. The flowers are zygomorphic, bell-shaped, drooping, sweet-scented, and have a slender, light green perianth tube that is 80–130 mm long and gently to strongly curved. The tepals are oblanceolate, 70–90 mm long and 15–20 mm wide, overlapping, and white with a pink median stripe on the outer surface. The tips of the tepals are strongly recurved. The stamens, are declinate (bent or curved downward), white, gradually turning pink at the apex, the anthers are black, the pollen is white. The style is rose pink, the stigma is tiny and pink.

The fruit is a capsule, globose, bright green, sharply beaked, and about 30 mm in width. The seeds are globe-shaped, light green, with a diameter of up to 10 mm.

The shape and colour of the flowers, the deeply channelled, glaucous leaves, and the beaked fruits bear resemblance to Crinum macowanii. However, the latter species is much more robust, with wider leaves (more than 40 mm wide) that form a pseudostem and are basally sheathed. It also has broader penduncles, non-ciliate leaf margins, larger flowers, fruits and seeds, and black pollen.