drop leaf
Refers to a hinged section of a table that can be raised or lowered. Common in furniture contexts.
このテーブルは垂れ板を上げると広くなる。
This table becomes larger when you raise the drop leaf.
Compound of 垂れ (tare, 'hanging') and 板 (ita, 'board'), referring to a board that hangs down when not in use.