lifeblood

• life blood, life's blood

life +‎ blood

lifeblood (usually uncountable, plural lifebloods)

1. Blood that is needed for continued life; blood regarded as the seat of life.

   Hypernym: blood

   • circa 1980, George Spelvin, Petticoat Loose, Act II, Scene 1, published in George Spelvin's theatre book, volume 3:

     You didn't come to me in time. And by the time you came to me that fool of a doctor had bled and leeched the lifeblood out of Timmy.

2. (figuratively) That which is required for continued existence or function.

   Synonym: essence

   Gasoline is the lifeblood of the modern city.

   • 2006, James E. Kibler, Memory's Keep, page 55:

     The road brought invaders who left them hungry and dug up the dead. The road took living children away and made them dead to home. It was as if the roads were veins that bled off lifeblood but never pumped it back in.