drop-in

Provided for short-term use.

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.

An alternative to cellulosic based second- generation biofuels are drop-in biofuels, that is, fuels such as synthetic gasoline that can be put into fuel tanks and pipelines with no modifications.

Allowing people to drop in; that is, to visit casually, without an appointment.

a drop-in centre

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.

One who casually drops in (visits unannounced or without appointment).

The office was efficient, but not well equipped to handle drop-ins.

An informal event that does not require booking in advance.

A place that can be visited casually, without an appointment.

The act of dropping in; that is, taking a wave that another surfer is already riding.

Drop-ins can and often do happen accidentally. Sometimes you're so focussed on your take-off that you just don't see the other rider.

A pitch that is prepared away from the ground or venue, and dropped into place only when a match is to be played.