blood circulation
Literal physiological sense; often used in set phrases like 血の巡りが良い/悪い.
Exercise improves blood circulation.
quickness of mind; apprehension
Figurative extension from blood circulation; almost always used in the negative phrase 血の巡りが悪い to mean slow-witted or dense.
See also: 血の巡りが悪い
He's slow on the uptake and doesn't get jokes.
Standard kanji-kana mixed spelling.
Kana spelling of 巡り; less common but still encountered.
Compound of 血 (blood) + の (possessive particle) + 巡り (circulation, going around). The figurative sense derives from the idea that poor blood flow to the head causes slow thinking.