1.
If you describe a supply of something as ~, you mean that it seems so large that it will never run out.
Princess Anne does not have a ~ purse.
ADJ
2.
If you describe something as ~, you mean that it is so deep that it seems to have no bottom.
His eyes were like ~ brown pools.
ADJ
3.
If you describe something as a ~ pit, you mean that it seems as if you can take things from it and it will never be empty or put things in it and it will never be full.
A gold mine is not a ~ pit, the gold runs out...
The problem is we don’t have a ~ pit of resources...
PHRASE