Webster's Revised Unabridged Dictionary · 1913

Sideling

Sideling , adverb

[Old English sideling, from side side. See Side, and compare Sidelong, Headlong.]

Sidelong; on the side; laterally; also, obliquely; askew.
A fellow nailed up maps... some sideling, and others upside down. — Swift

Sideling , adjective

Inclining to one side; directed toward one side; sloping; inclined; as, sideling ground.