Yes, ordnance is a word. Before you revert my edits please note:
Per merriam webster (https://www.merriam-webster.com/dictionary/ordinance) ordinance (with an "i") is defined as authoritative order or degree. While ordnance (without an "i") is defined as military supplies including weapons, ammunition, combat vehicles, and maintenance tools and equipment (https://www.merriam-webster.com/dictionary/ordnance)