From Longman Dictionary of Contemporary Englishhorsebackhorse‧back /ˈhɔːsbæk $ ˈhɔːrs-/ noun → on horseback —horseback adjective [only before noun]
Examples from the Corpus
horseback• But trees have managed to grow on the banks, and the sandy beds are ideal for horseback riding.• A moment or two afterward I was almost alone on horseback in the open field between the two lines of battle.• The bride and groom arrived on horseback.• The wars of this period presented little opportunity to shock troops fighting on horseback.• At odds of 10-1 he bet a hundred pounds he could complete 200 miles in less than nine hours on horseback.• It did no harm that he also had an engaging way about him and made a dashing picture on horseback.• In comparison, she herself would look little better than a sack of potatoes on horseback.• The tours will feature helicopter rides, horseback treks and river rafting. 