A plateau is high, flat ground or a situation where something has stalled that was progressing forward previously. An example of a plateau is a high, flat field. An example of a plateau is a situation where no progress is being made on a project while you await funding approval. The definition of a plateau is high, flat ground or a situation where something has stalled that was progressing forward previously. An example of plateau is when a project stalls and can't move forward because decisions cannot be made.