lower seat; seat at the bottom of the table
Refers to the seat farthest from the entrance or the seat of lower status in a traditional Japanese room, often near the door or at the foot of the table.
宴会では新人が下座に座ることが多い。
At banquets, newcomers often sit in the lower seat.
お客様を上
I seat the guest in the seat of honor and take the lower seat myself.
Compound of 下 (しも, 'lower') and 座 (ざ, 'seat'). The reading しもざ follows rendaku voicing of 座.