Step or sliding step (towards uke), followed by a turn on one foot.
This entry is very typical for aikido, and used in many techniques. Usually, the contact to uke is established at some point during the tenkan turn.
Irimi-tenkan is closely related to the principle of awase: defence techniques are never purely passive, they always contain an element of actively meeting the attacker (irimi), in the sense of showing initiative and acting a moment earlier than uke.
