plural of proof by contradiction

A legal requirement to achieve an impossible proof. Remedies are reversing the burden of proof, or giving additional rights to the individual faced with this requirement.

(logic) A proof showing that if an assumption A is true then a consequent statement or conclusion B must also be true, i.e. B is true on the condition that A is true.

Alternative spelling of proof of concept

airtight

Intensely; strongly.

(US) Used other than figuratively or idiomatically: 55% alcohol by volume. / (idiomatic) Stronger than strong.

plural of burden of proof

Alternative spelling of leakproof

(law, of a defendant) Exempt from the payment of debts, either because of insufficient funds or because of protection by statute.