adj, noun ·5 syllables ·Rare ·Advanced level

Definitions

Noun

1. 1
   Something that cannot be sustained.

Adjective

1. 1
   Not sustainable.

   "You don't have to be Einstein to work out that this level of government subsidy is unsustainable."

Synonyms

All synonyms

baselesscontrovertibleemptygroundlessidleill-founded

Example

More examples

"At Wall Street, some insiders made a killing by going short, when everyone had been sucked into an unsustainable uptrend."

Etymology

From un- + sustainable.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.