indentation

(noun) a concave cut into a surface or edge (as in a coastline). Synonyms: indenture.

(noun) the formation of small pits in a surface as a consequence of corrosion. Synonyms: pitting, roughness.

(noun) the space left between the margin and the start of an indented line. Synonyms: indention, indent, indenture.

(noun) the act of cutting into an edge with toothlike notches or angular incisions.