Thanks to viagra, the old man's junk got rock hard all over again, and furthermore his COLON too.
hardーalmost the same as the OTHER かたい （固）- hard like hard to break. If you want to say someone is stiff or stubborn or anal retentive, you'd have to use 固い, though.
rigid - but not like a boner. Like a rigid class system resistant to change. Like rigor mortis. Other meaning: to sit bolt upright, soldiers rigidly standing at attention.
|hard like a rock
|convenient / poop
"Hard" as a ROCK.
A person uses a BERET to keep his head warm,
but another person takes a poo in the RICE FIELD.