indentation, indenture, dent, notch, undercut, cutmark, kerf, birdsmouth, serration, scarf, more...

outdent

space, gap, break, incision, slit, notch, dent, depression, more...

first, left, line, right, second, third, deep, small, negative, fourth, slightest

bend inward,   make a dent,   dent slightly,   protrude inward,   soft dent,   anchor space,   notch down,   groove in,   to add whitespace