side altar
an altar subordinate to the high altar, typically at the head of a side aisle, along the sides of the nave, or in a bay or chapel
en-GB/ˈsaɪd ˈɒltə/
en-US/ˈsaɪd ˈɔltɚ/
an altar subordinate to the high altar, typically at the head of a side aisle, along the sides of the nave, or in a bay or chapel