godan verb (-mu), intransitive verb
lean to one side; oppose; look aside; regret
Rare archaic verb. The core image is turning or leaning away from something, giving rise to the extended meanings of opposing, looking away, and regretting. Modern Japanese uses 傾く, 反対する, 横を見る, 後悔する instead.
古語では「そばむ」は「かたむく」や「そむく」の意で使われた。
In classical Japanese, そばむ was used to mean 'to lean' or 'to oppose'.
The historical derivation is uncertain; the kanji 側 (side) is conventionally associated with the meaning of leaning or turning aside.