A pratfall is a mistake that is particularly embarrassing, like going to a job interview with stains on your shirt. It can also be a silly goof done on purpose to make people laugh, like slipping on a banana peel.
A pratfall originally referred to a fall on your butt, which was often done by comic actors for laughs. From there, it came to mean all sorts of unplanned screw-ups. A restaurant caught serving horsemeat has committed a pratfall. A politician’s inappropriate joke is a verbal pratfall. A football player who runs the wrong way and scores for the other team has done a pratfall. Oops!