bottomless

Having no bottom.

The vast swamps of Southern Ontario proved a grim nightmare to the construction gangs. Treacherous and seemingly bottomless, the swamps swallowed thousands of tons of timber and debris, yet still afforded no firm surface on which the track could be laid.

And while the railway's finances will forever remain a bottomless black hole, Highways England finances are rapidly becoming a bottomless pothole!

Extremely deep.

Having no bounds; limitless.

The restaurant offered bottomless drinks.

Of a meal: accompanied by unlimited drinks.

I get a message from some school friends about a bottomless brunch they want to go to.

Difficult to understand; unfathomable.