A guess or hunch, often based on intuition or experience rather than solid evidence. Frequently used in phrases like 山勘が当たる (the guess is right) or 山勘で言う (say based on a hunch).
His hunch was right, and he won the lottery.
I answered based on a guess, and it happened to be correct.
Standard kanji spelling.
Katakana spelling is common in casual writing.
Search-only mixed kanji-katakana form.
The origin is disputed. A leading explanation treats it as a shortening of 山師の勘, “a prospector’s intuition,” referring to a guess made without firm evidence.