A multiple loop space.
A grouplike E-k algebra in Top.
An iterated loop space object in Top.
Peter May, Infinite loop space theory, Bull. Amer. Math. Soc. Volume 83, Number 4 (1977), 456-494. (Euclid)
Infinite loop space theory revisited (pdf)
John Adams, Infinite loop spaces, Herrmann Weyl lectures at IAS, Princeton University Press (1978)
Section 5.1.3 of