What is transimpedance?
Impedance means a circuit element that produces a voltage when a current is applied.

For example, if you apply 1 A to a 1 Ohm resistor, 1 V will be generated across the resistor.

Transimpedance applies to a 2-port (or n-port) device, rather than a simple single-branch circuit element, and it means the two-port produces a voltage when a current is applied, but the voltage appears on a different port than the current was applied to. 

Describing a device with a transimpedance means you're describing the device as a CCVS (current-controlled voltage source). Like an ordinary impedance, the units of a transimpedance are ohms (V/A).

As an example, a transimpedance amplifier produces a voltage at its output when a current is provided to its input.