We don't have synonyms for unlap yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are unlax, uncap and unlaw.
(v) :
(intransitive, usually reflexive, motor racing) To overtake the leader in a race in order to no longer be lapped (one or more complete laps behind the leader).
(v) :
(intransitive, usually reflexive, motor racing) To overtake the leader in a race in order to no longer be lapped (one or more complete laps behind the leader).