'pig-a-back' definitions:

Definition of 'pig-a-back'

(from WordNet)
adverb
On a railroad flatcar; "the trailer rode piggyback across the country" [syn: piggyback, pickaback, pig-a- back]
adverb
On the back or shoulder or astraddle on the hip; "she carried her child piggyback" [syn: piggyback, pickaback, pig-a- back]