Synonyms for Indentation (same or very similar meaning)
WordNet sense 1 (a concave cut into a surface or edge (as in a coastline)):
indenture
WordNet sense 2 (the formation of small pits in a surface as a consequence of corrosion):
roughness, pitting
WordNet sense 3 (the space left between the margin and the start of an indented line):
indent, indention, indent
From the ODE community, based on WordNet
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