1. Any force or influence that consists of a quantity which is specified by magnitude, direction, and sense: The vector of the aircraft consisted of elements that the pilot had to maintain in order to arrive safely at his destination on time.
2. An organism; such as, a mosquito or a tick, that carries disease-causing microorganisms from one host to another one: A vector picks up disease organisms from sources of infections from infected blood or feces, carries them inside or on their bodies, and then deposits them where they infect a new host, either directly or indirectly.

A vector can be any agent (person or animal or microorganism) that carries and transmits a disease. For example, mosquitos are vectors of malaria, West Nile virus, and yellow fever and fleas are vectors of the plague. Aphids are transmitters of plant diseases. When medical scientists refer to vectors they are usually talking about insects.

3. A bacteriophage, plasmid, or other agent that transfers genetic material from one cell to another cell: Genetic engineering relies on the use of vectors when creating or cloning cells.
4. A computer memory location containing the address of a code; usually, some kind of operating system service: By changing the vector to point to a different piece of code, it is possible to modify the behavior of the operating system of a computer.

To guide someone or something: A pilot or an aircraft is vectored by using radio communications.

A radio transmitter was vectoring the hikers towards safety after they got lost in the jungle.