Lewis & Short

sur-rustĭcus (subr-), a, um, adj., somewhat clownish or rustic: sonare subagreste quiddam planeque surrusticum, Cic. Brut. 74, 259; id. Or. 48, 161: pudor quidam paene surrusticus, id. Fam. 5, 12, 1.
* Adv.: surrustĭcē, somewhat clownishly, Gell. praef. § 10.