backsies

back +‎ -sies

backsies (uncountable)

1. (childish) The act of taking back or going back on one's word, promise, or gift.
   • 1987, Carolyn W. Field, Jaqueline Shachter Weiss, Values in selected children's books of fiction and fantasy

     Frances is the loser when she agrees to no "backsies" or refunds as she buys Thelma's plastic tea dishes with money saved for a china set.

   • 2008 March 25, Harvey Araton, “For President, Knicks Could Look Nearby”, in New York Times‎:

     Not one to gloat, Thorn did sound amused Monday when asked if he had broken the news to the Mavericks’ owner, Mark Cuban: no backsies.

   • 2011, Jenna Katerin Moran, Nobilis: The Essentials, Volume 1, page 11:

     Then you will be in trouble because it will kill you to have it taken out again but it will betray your deepest inner truth to tell them No Backsies.

2. (childish) A reciprocal action or consequence, such as immediately tagging the player who has tagged one in a game of tag.