A term sometimes used for a rate coefficient. For example, if the rate equation is:
the function
is the pseudo first-order rate constant (or first-order rate coefficient) with respect to B. Similarly,
is the pseudo first-order rate constant (or first-order rate coefficient) with respect to A. The term pseudo rate constant is particularly useful when the concentration of one reactant is much greater than
that of another.

See also: rate coefficient

Source:

PAC, 1996, *68*, 149*
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC
Recommendations 1996))
* on page 178