Echinopsis clavatus grows shrubby, branches from the base and is more or less prostrate and creeping. The club-shaped, dark green shoots are 1 to 2 meters long and have a diameter of with seven to ten blunt ribs that are notched. The roundareoles are densely covered with orange-brown wool and are apart. Dark brown, needle-like, mostly straight spines emerge from them. The usually single, very strong central spine is long and four to eight slightly spread out radial spines are long. The funnel-shaped, white flowers reach a length of up to.
The first description by Friedrich Ritter was published in 1980 as Trichocereus clavatus. The specific epithet clavatus comes from Latin, means 'club-shaped' and refers to the shape of the shoots.