This is the 14617th most frequent Turkish word.
pizzayı
"Pizza" (direct object form in Turkish; accusative case).
Here, 'pizzayı' is in the accusative case as the direct object of the verb 'severim'.
Pizzayı çok severim.
I like pizza very much.
In this sentence, 'pizzayı' indicates specifically 'the pizza' that was mentioned or known beforehand due to the use of the definite accusative form.
Pizzayı dün akşam yedik.
We ate the pizza last night.
'Pizzayı' functions as the definite object in this question, specifying the pizza being referred to with the definite accusative case.