noun
reverse side; back; other side; hidden side; behind the scenes
Colloquial noun for the opposite or hidden side of something, both physically and figuratively. Often implies a less visible or secret aspect. Compare with 裏側 (うらがわ), which is more standard and neutral.
See also: 裏側
この布、裏っ側はもっと柔らかいんだよ。
The reverse side of this cloth is even softer.
彼はいつも裏っ側の事情を探ろうとする。
He always tries to find out the behind-the-scenes circumstances.
More standard and neutral term for the reverse or back side. 裏っ側 is a colloquial variant with a slightly more informal or emphatic feel.
Colloquial form derived from 裏側 (うらがわ) by inserting a small-tsu (っ) for emphasis or casual effect. The exact origin is uncertain, but it likely arose in informal speech.