Foundationless and Low-down

Foundationless adjective - Having no basis in reason or fact.

Low-down and foundationless are semantically related. In some cases you can use "Low-down" instead an adjective "Foundationless".

Low-down adjective - Not following or in accordance with standards of honor and decency.

Foundationless and low-down are semantically related. Sometimes you can use "Foundationless" instead an adjective phrase "Low-down".