Decumanus Maximus is a term in ancient Roman city planning. It denotes a E-W oriented road in a Roman military camp or colonia. The main decumanus is the Decumanus Maximus that normally connects the Porta Pretoria (in a military camp, closest to the enemy) to the Porta Decumana (away from the enemy). In the middle the Decumanus Maximus crosses the perpendicular Cardus Maximus, the other main road. The Forum is normally located at this intersection of the Decumanus Maximus and the Cardus Maximus.
The term 'decumanus' is derived from the E-W line the augurs would draw when making the auspices.
