Pre-teaching is the teaching of the language learners need before an activity.

Example
The learners are going to hear a short discussion on environmental issues. Before listening, they match key environment words to definitions.

In the classroom
In order to pre-teach vocabulary effectively, the teacher needs to identify what their learners already know and what might cause problems. Although course books often provide this information in pre-teaching stages, many teachers take time when planning to identify problem areas.