Lewis & Short

tantis-per, adv. [tantus], for so long a time, so long; in the mean time, meanwhile.

        1. (α) With dum (class.): ego hic tantisper, dum exis, te opperiar foris, Plaut. Most. 3, 1, 153: meretrix tantisper blanditur, dum illud, quod rapiat, videt, id. Men. 1, 3, 11: tantisper volo, Dum facies, Ter. Heaut. 1, 1, 54: ut ibi esset tantisper, dum culeus compararetur, Cic. Inv. 2, 50, 149: latendum tantisper ibidem, dum defervescat haec gratulatio, id. Fam. 9, 2, 4.
        2. (β) With quoad (post-class.): ut viveret tantisper, quoad fieret permutatio, Gell. 6, 4, 1: agere tantisper, quoad de servitute constet, Dig. 43, 18, 3 fin.
        3. (γ) Absol. (class.): ego hic astabo tantisper, Plaut. Mil. 4, 2, 30: tantisper hic ego ad januam concessero, id. Aul. 4, 5, 6: totos dies scribo, non quo proficiam quid, sed tantisper impedior, Cic. Att. 12, 14, 3; id. Caecin. 10, 30: sed videro, quid efficiat: tantisper hoc ipsum magni aestimo, quod pollicetur, id. Tusc. 5, 7, 19: tantisper tutelā muliebri res Latina puero stetit, Liv. 1, 3, 1; 1, 22, 5.