What do you mean by pseudo unimolecular reactions?

Pseudo unimolecular reactions:
Consider the following acid catalysed reactions:
1. Hydrolysis of ethyl acetate:
CH₃COOC₂H₅ + H₂O + H⁺ ———–>CH₃COOH + C₂H₅OH

2. Inversion of cane sugar:
C₁₂H₂₂O₁₁ + H₂O + H⁺ —————> C₆H₁₂O₆ + C₆H₁₂O₆

Both the above reactions are bimolecular but are found to be of first order, as experimentally it is observed that:
For the first reaction, the rate of reaction α [CH₃COOC₂H₅] only
And for the second reaction, the rate of reaction α [C₁₂H₂₂O₁₁] only
The reason for such a behavior is obvious from the fact that water is present in such a large excess that its concentration remains almost constant during the reaction.

Such reactions which are not truly of the first order but under certain conditions become reactions of the first order are known as pseudo unimolecular reactions.