down bubble

Etymology
From the bubble of air in the glass tube of the inclinometer, a gauge that indicates the submarine's vertical trim.

Adjective

 * 1)  having a downward trim (of a submarine); usually follows the number of degrees
 * 2) * 2000, Overdue and Presumed Lost, by Arthur MacMahan, page 181
 * Dissatisfied with Sailfin's sluggish response, he turned the iron wheel a bit more until the bubble rode backward, indicating that the submarine's stern had lifted relative to the dipping bow. A glance at the calibrations etched into the brass plate behind the liquid-filled glass tubing told him that Sailfin's nose has dipped the required amount. "We have ten degrees down bubble, sir."
 * Dissatisfied with Sailfin's sluggish response, he turned the iron wheel a bit more until the bubble rode backward, indicating that the submarine's stern had lifted relative to the dipping bow. A glance at the calibrations etched into the brass plate behind the liquid-filled glass tubing told him that Sailfin's nose has dipped the required amount. "We have ten degrees down bubble, sir."

Translations

 * Russian: с диффере́нтом на́ но́с