Lewis & Short

sŭbactĭo, ōnis, f. [subigo].

  1. I. Lit., a working through, working up, preparing (rare): harena fluviatica bacillorum subactionibus in tectorio recipit soliditatem, Vitr. 2, 4 fin.: subactiones ciborum, Arn. 3, 107.
  2. * II. Trop., preparation, discipline: subacto mihi ingenio opus estsubactio autem est usus, auditio, lectio, litterae, Cic. de Or. 2, 30, 131.