water-bath still
From The Oxford Companion to Spirits & Cocktails
is a modification of a standard pot still, often used for distilling cordials, in which a separate vessel is placed inside the water-filled still pot (similar, in principle, to a double boiler or bain-marie). See also cordials, still, pot.
This definition is from The Oxford Companion to Spirits & Cocktails, edited by David Wondrich (Editor-in-Chief) and Noah Rothbaum (Associate Editor).