Lewis Short
(adverb) : tantis-per, tantus
* For so long a time, so long; in the mean time, meanwhile.
* 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.
* 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.
* 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.
Charlton T. Lewis, Charles Short, A Latin Dictionary