Trigunasamyavastha is the balanced state of the three gunas – Sattva, Rajas and Tamas. This is the state before the beginning of creation and is also known as mulaprakriti. If this state had lasted indefinitely, and there was no change in it, then creation would have been impossible.
In the Trigunasamyavastha state, the three gunas are in a perfectly balanced state, none of them taking the upper hand or dominating and suppressing the other two. The result of balanced forces makes for stability, balance, perfect peace and complete stoppage of movement or action in any direction.
The original peace and balance is disturbed by Purusha and this result in creation. First sattva guna gains the upper hand. Once the balanced state of the three gunas is disturbed it results in an endless cycle of creation. The creation and activity comes to and only when once again the three the gunas enter into a balanced state.
The goal of a spiritual aspirant is to enter into this balance state.