。
Whenever Nomo strikes out a batter, the crowd goes wild.
Literal
Nomo [subj-が] batter [obj-を] stifle-[cond-と] spectator [subj-が] is-rising-up-[polite-ます].
A reference to Nomo Hideo, the legendary Japanese pitcher who became a star with the Los Angeles Dodgers in the 1990s. The conditional ~と here is habitual ('whenever X, then Y'). わきあがる ('erupt, rise up') is used for crowds cheering, emotions surging, and applause swelling — a vivid physical-image verb.