to make foul, dirty, or unclean; pollute; taint; debase.
2.
to violate the chastity of.
3.
to make impure for ceremonial use; desecrate.
4.
to sully, as a person's reputation.
Origin: 1275–1325; Middle English defilen, defelen, alteration of defoilen (by association with filen to file3) < Anglo-French, Old French defouler to trample on, violate; compare Old English befȳlan to befoul
to tarnish or sully the brightness of; taint; corrupt
3.
to damage or sully (someone's good name, reputation, etc)
4.
to make unfit for ceremonial use; desecrate
5.
to violate the chastity of
[C14: from earlier defoilen (influenced by filen to file³), from Old French defouler to trample underfoot, abuse, from de- + fouler to tread upon; see full²]
"narrow passage," 1640s, especially in a military sense, "a narrow passage down which troops can march only in single file," from Fr. défilé, n. use of pp. of défiler "march by files."