No!! These, too, are kanji!!
The combination of the two characters is read でこぼこ (dekoboko), and it means, “unevenness“. It is commonly used for example to describe a road that has a lot of bumps or depressions ( 凸凹な道, でこぼこなみち).
Thy can also be read separately.
凸 (でこ, deko) -> forehead
凸 (とつ, totsu) -> convex
凹 (おう, ou) -> concave
凹 (くぼ, kubo) -> cavity
凹む (へこむ, hekomu) -> to be dented, to feel down
凹み (へこみ, hekomi) -> hollow, depression
凹田 (くぼた, kubota) -> rice field in a low place
凹凸 (おうとつ, outotsu) -> unevenness (same meaning)