drop-in

(not comparable)Provided for short-term use.

(not comparable)Fit to substitute for some element in a complex system without changes to the existing infrastructure.

We need the ultimate drop-in biofuel to make use of our expensive oil-based infrastructure.

(not comparable)Allowing people to drop in; that is, to visit casually, without an appointment.

a drop-in centre

(not comparable)Of the pitch: prepared away from the ground or venue, and dropped into place only when a match is to be played.

The pitch at the Melbourne Cricket Ground is drop-in, and the ground is also used for Australian rules football.