n. 巨石牌坊

Trilithon \Tril"i*thon\ (tr[i^]l"[i^]*th[o^]n), n.; pl.
{Trilithons}. [NL., fr. Gr.? of or with three stones; ? (see
{Tri-}) + ? stone.] (Arch[ae]ol.)
A monument consisting of three stones; especially, such a
monument forming a kind of doorway, as among the ancient
Celts.