A rehearsal that focuses on adapting to the actual performance space, including stage layout, acoustics, and lighting, rather than just running lines.
See also: 場当たり (ばあたり)
Tomorrow we have a dress rehearsal at the hall.
In the dress rehearsal, we check the actual size of the stage.
場当たり is a broader term meaning 'playing to the gallery' or 'ad-libbing according to the situation', while 場当たり稽古 specifically refers to a rehearsal that adapts to the performance space.
Compound of 場当たり (adapting to the venue) and 稽古 (practice, rehearsal).