balloon — OET

balloon

noun

hot-air balloon, fire balloon, barrage balloon, weather balloon;

airship, dirigible, Zeppelin, Montgolfier;

envelope, gasbag;

informal blimp.

verb

1 the slack sail was ballooning in the squall:

swell (out), puff out/up, bulge (out), bag, belly (out), fill (out), billow (out);

blow up, inflate, distend, expand, dilate.

▷antonyms sag, flap.

2 the company's debt has ballooned in the last five years:

increase rapidly, soar, rocket, shoot up, escalate, mount, surge, spiral, grow rapidly, rise rapidly;

informal go through the ceiling, go through the roof, skyrocket.

▷antonyms plummet.

balloon Oxford Dictionary of English