401(k)
noun
ˌfȯr-(ˌ)ō-(ˌ)wən-ˈkā 
: a retirement account to which employee and employer contribute, on which taxes are deferred until withdrawal, and for which the employee usually selects the types of investments
Word History
Etymology
from the section of the Internal Revenue Code that established it
First Known Use
1980, in the meaning defined above