за́йцем
adverb
usually with ехать
without paying, for free
за́яц
conversational
stowaway; gate-crasher
е́хать за́йцем
travel without paying for a ticket; take a free ride; stow away
conversational
one who uses public transportation without buying a ticket, fare dodger, stowaway
ехать зайцем
to be a stowaway
(lit. “to ride as a hare”)
used in the following idiomatic expressions