Drop-in

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.

a drop-in centre

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

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

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.