noun
short-lived company; fly-by-night company
Refers to a company that is set up quickly and likely to fail or disappear soon, often with a connotation of unreliability.
あのベンチャーは結局泡沫会社に終わった。
That startup ended up being just a short-lived company.
泡沫 means 'bubble' or 'foam', and metaphorically something transient or insubstantial. 泡沫会社 specifically applies this to a company.
Compound of 泡沫 (ほうまつ, 'bubble, foam', metaphorically something fleeting) and 会社 (がいしゃ, 'company').