Firm and not easily bent, cut, or broken

• Resistant to pressure or penetration

Not easy to do, understand, or solve

• Requiring a lot of effort

With great effort, intensity, or force

Containing alcohol, as of beverages

Severe or harsh in effect or manner

• Difficult to endure

Of water, high in dissolved minerals, especially calcium and magnesium

In physical form rather than digital; involving hardware or manual action

Definite, objective, and verifiable; based on facts rather than opinion