a quick examination of a few members of a group instead of the whole group

The police are doing spot checks on motorists to test alcohol levels. 警方正在对司机进行现场抽查，检测是否有人酒后开车。

to quickly examine a few members of a group instead of the whole group

Inspectors spot-checked stores countywide. 检查人员在全县范围内抽查商店。

At park exits vehicles are spot-checked by an armed ranger. 在公园出口处，武装护林员对车辆进行抽查。