Sub"stit"ute (?), n. [L. substitutus, p. p. of substituere to put under, put in the place of; sub under + statuere to put, place: cf. F. substitut. See Statute.] One who, or that which, is substituted or put in the place of another; one who acts for another; that which stands in lieu of something else; specifically (Mil.), a person who enlists for military service in the place of a conscript or drafted man.

Hast thou not made me here thy substitute?

Ladies [in Shakespeare's age] . . . wore masks as the sole substitute known to our ancestors for the modern parasol.

Sub"stit"ute (?), v. t. [imp. & p. p. Substituted (?); p. pr. & vb. n. Substituting (?).] [See Substitute, n.] To put in the place of another person or thing; to exchange.

Some few verses are inserted or substituted in the room of others.

Sub"stit"ute (?), n. [L. substitutus, p. p. of substituere to put under, put in the place of; sub under + statuere to put, place: cf. F. substitut. See Statute.] One who, or that which, is substituted or put in the place of another; one who acts for another; that which stands in lieu of something else; specifically (Mil.), a person who enlists for military service in the place of a conscript or drafted man.

Hast thou not made me here thy substitute?

Ladies [in Shakespeare's age] . . . wore masks as the sole substitute known to our ancestors for the modern parasol.

Sub"stit"ute (?), v. t. [imp. & p. p. Substituted (?); p. pr. & vb. n. Substituting (?).] [See Substitute, n.] To put in the place of another person or thing; to exchange.

Some few verses are inserted or substituted in the room of others.

• to replace with something that should function the same way
  
• a replacement or stand-in for something that achieves a similar result or purpose.