The Picasso triggerfish showcases a robust, oval body adorned with a mesmerizing array of colors and markings. Growing up to 50 centimeters in length, its body features a backdrop of dark blue or black, overlaid with bold, yellowish stripes and spots that create a striking contrast. Its most distinctive feature is the large, diagonal yellow stripe running from the eye to the mouth, resembling a painted brushstroke. The fish's strong jaws are equipped with sharp, chisel-like teeth, ideal for cracking open the hard shells of crustaceans, mollusks, and sea urchins—its primary prey. Additionally, it possesses a unique fin structure: a retractable first dorsal spine, which it can lock into place for defense, and a second spine that serves as a "trigger" to release the first, giving the species its name.

In its natural habitat, Rhinecanthus aculeatus is territorial and highly protective of its nesting sites, particularly during the breeding season. While solitary for much of the year, it exhibits fierce aggression when threatened, using its spines and powerful bite to fend off predators and intruders. Divers approaching its nesting area may encounter defensive charges, highlighting the fish's tenacity. Despite its feisty nature, the Picasso triggerfish plays a vital role in reef ecosystems by controlling invertebrate populations and preventing overgrowth of sea urchins, which can damage coral. However, like many reef-dwelling species, it faces threats from habitat degradation due to coral bleaching, overfishing, and the aquarium trade. Conservation initiatives, including marine protected areas and sustainable fishing practices, aim to preserve this iconic triggerfish and maintain the health and diversity of the world’s coral reefs.