Stiff
Stiff turns up in 2 fields: electrotechnology, maritime. Here is what it means to the people in each one.
Stiff in electrotechnology
Describes a supply with low source impedance, so its voltage barely moves when load or fault current changes.
A stiff source or stiff bus has a high short-circuit level compared with the load connected to it, so motor starts, load steps and harmonic currents cause little voltage change. Engineers use the word as shorthand for a high short-circuit ratio: a 400 kV bus fed from several large stations is stiff, while a long rural feeder or a small island grid is soft or weak. Stiffness helps voltage quality but raises fault current and the duty on switchgear.
"The 33 kV bus at the smelter is stiff enough that a 2 MW motor starting direct-on-line barely flickers the lights."
Stiff in maritime
Describing a strong wind or a vessel that snaps back upright too quickly.
Used to describe a strong, steady wind that puts heavy pressure on the sails. In naval architecture, a stiff vessel has a very low center of gravity, causing it to resist heeling and snap back violently from a roll. While a stiff ship is highly stable and unlikely to capsize, the aggressive rolling motion is uncomfortable for the crew and can damage cargo or rigging.
"She's riding a bit stiff since we loaded all that dense steel in the lower hold."