O

/oʊ/

Definitions of O

1. noun

   the 15th letter of the Roman alphabet
   synonyms: o

   type of:

   alphabetic character, letter, letter of the alphabet

   the conventional characters of the alphabet used to represent speech
2. noun

   a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
   synonyms: atomic number 8, oxygen

   types:

   LOX, liquid oxygen

   a bluish translucent magnetic liquid obtained by compressing gaseous oxygen and then cooling it below its boiling point; used as an oxidizer in rocket propellants

   type of:

   chemical element, element

   any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter

   gas

   a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
3. noun

   the blood group whose red cells carry neither the A nor B antigens
   synonyms: group O, type O

   type of:

   blood group, blood type

   human blood cells (usually just the red blood cells) that have the same antigens