Covered with or abounding in trees; having the characteristics of trees or forests.
From Latin 'arbor' (tree) with the English suffix '-ous' (full of, characterized by), creating an adjective that describes landscapes or regions dominated by tree growth.
This is an older, poetic way to describe a forest landscape—you might read it in Victorian nature writing, and it perfectly captures that sense of being surrounded by a canopy of branches above you.
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