"Clunky dialogue" refers to dialogue in a book, movie, or other form of storytelling that feels awkward, unrealistic, or poorly written. Full definition
Somewhere within the bleak gray tones of «Dark Crimes» is an interesting story, but its overwhelmed by a familiar characters and plot lines with clunky dialogue, unfortunately. (keeping-it-reel.com)
Lots of solid action, a bit of clunky dialogue... but you know what? (firstshowing.net)
There's a germ of a smart biopic in Diana; the problem is that it's tucked away behind a clunky structure and even clunkier dialogue. (rottentomatoes.com)