It is a mocking way to say 'speaking Spanish'.
E.g. Long ago in my village everybody spoke Valencian, now most of the people speak in ocho.
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És una manera burlesca de dir «parlar en castellà»
Ex. Abans al meu poble tot el món parlava valencià, ara quasi tots parlen en ocho.
Linguistic clarifications:
*Ocho is the number eight in Spanish.
