reverse; inversion; upside down
Describes something being the opposite way around, inverted, or turned upside down. Can be used literally or figuratively.
The photo is upside down.
The picture was hung upside down.
What he says is always the reverse of the truth.
Used for ideas, arguments, or situations that are contrary to reason or common sense. Often implies a perverse or twisted logic.
Such absurd reasoning won't hold water.
I put my shoes on backwards.
His story is the exact opposite of the truth.
That's a twisted, absurd way of thinking.
反対 describes a neutral positional or directional opposite, whereas 逆しま often implies a more thorough, upside-down or morally twisted reversal.
あべこべ is a colloquial way to say two or more things are mixed up in reversed order, while 逆しま is more literary and can apply to a single thing being inverted.
理不尽 focuses on something being unjust or illogical, while 逆しま (in this sense) stresses that the logic itself is twisted or backwards.
Standard kanji spelling; the okurigana しま makes the reading clear.
Rare kanji form; the reading さかしま is not obvious from this character alone.
The word さかしま is derived from 逆 (さか, 'reverse') + しま, an old suffix indicating direction or state. The kanji 逆しま is a standard spelling, while 倒 is a rare alternative.