It seems like Data was over-explaining what was happening in response to another captain describing the distortion as a hiccup.
Seems like that specific “body function” was never made clear in the show itself.
According to this transcript, this the entire context of the conversation in which Data attempted to make an analogy; bold emphasis in dialogue is mine:
RIKER: Captain, we've received communication from the freighter Lalo, as well as from a farming colony on Coltar Four. Both described the same time distortion. The Captain of the Lalo described it a hiccup.
DATA: Actually sir, that may be an incorrect analogy.
PICARD: How so, Data?
DATA: A hiccup is a spasmodic inhalation with closure of the glottis. accompanied by a peculiar sound. If we were to continue this analogy to a body function, what occurred would be best represented by a
PICARD: That's enough, Data. Have you been able to learn more specifics about the Manheim project?
So Data went on rambling, Picard cut him off and that’s that. One can assume any specifics past what was outlined in the show/script is just speculation.