1. rowdy or boisterous play
The Collaborative International Dictionary of English v.0.48:
Horseplay \Horse"play`\, n.
Rude, boisterous play.
Too much given to horseplay in his raillery. --Dryden.
WordNet (r) 3.0 (2006):
n 1: rowdy or boisterous play
Moby Thesaurus II by Grady Ward, 1.0:
33 Moby Thesaurus words for "horseplay":
badness, banter, buffoonery, clownishness, discourtesy, disorder,
disorderliness, disorderly conduct, disruption, disruptiveness,
foolery, fooling, frowned-upon behavior, harlequinade, hooliganism,
impropriety, misbehavior, misconduct, misdemeanor, misdoing,
monkeyshines, naughtiness, nonsanctioned behavior, roughhouse,
rowdiness, rowdyism, ruffianism, shenanigans, tomfoolery,
vandalism, venial sin, vice, wrongdoing