Beijing-flavored colloquial — the
儿化 (érhuà) ending is essential and pronunciation is roughly "gāo-gèr" (one syllable, with the
儿 just coloring the tongue). Compare with the formal/written
高个子 (gāogèzi) which means the same thing without the Beijing flavor. The opposite is
矮个儿 (ǎigèr, "short one").