(idiomatic) To be particularly, especially uncannily, observant; a perceived ability to see in all directions at once.

Without sympathy, feeling or compassion; callous or heartless

(obsolete) Da Costa's syndrome, a disorder of the heart related to combat.

With the head in front; headlong. / Rashly; precipitately; without deliberation; hastily.

With the head in front; headlong.

Adjectival or attributive form of angels dancing on the head of a pin.

(figuratively) The subject of arcane intellectual speculation; used as an example subject of enquiry the pursuit of which is of no value.

Alternative spelling of clearheaded

(thermodynamics) The heat capacity per unit mass

Having the traditional shape of a heart (♥), that is pointed at one end and indented at the opposite side.