The Collaborative International Dictionary of English v.0.48:

Leaseholder \Lease"hold`er\, n.
   A tenant under a lease. -- Lease"hold`ing, a. & n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

leaseholder
    n 1: a tenant who holds a lease [syn: leaseholder, lessee]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "leaseholder":
   hirer, homesteader, incumbent, lessee, lodger, occupant, occupier,
   paying guest, renter, resident, roomer, squatter, sublessee,
   subtenant, tenant, tenant at sufferance, tenant for life,
   underlessee