The character 凸 visually looks like something protruding upward from a flat surface - a perfect pictograph!
usage
Opposite of 凹 (concave). The pair 凸凹 or 凹凸 means uneven/bumpy.
Components
pictograph
凸tū
protruding; convex
Pure visual pictograph - the silhouette itself is the meaning: a flat baseline with a raised central platform jutting upward, the literal outline of a bump. Pairs with 凹 (concave) to form one of the most iconic visual pairs in the script. Indexed under Kangxi #17 凵 by tradition; no clean 凵-element separates here.
Filed under radical 凵 (kǎn, #17) by convention. 凵 is not a separate component in 凸, so no strokes are highlighted.
