1. to go beyond what is expected
push the boundaries of science/knowledge
To 'push' something mean to exert pressure on something in order to move something forward or away from yourself. To 'expand' means to make something larger or enable something to extend. A 'boundary', 'frontier' or 'limit' is a designated barrier. If you push or expand beyond the boundaries, frontiers or limits of something or somewhere you aim to extend beyond the established norms or constrains of something. If you expand beyond boundaries, frontiers or limits you manage to succeed in passing the recognised boundaries into new areas or new ground.
The artist Salvador Dali really pushed the boundaries of Surrealism.