Uneven means not level, or not equal. An uneven floor, uneven performance, uneven distribution.
Of a surface it means bumpy and hard to walk on, and uneven ground is the standard warning. Of quality it means inconsistent — an uneven performance had good passages and bad ones, which is a real and useful criticism. Of a share it means unequal. Note that uneven is Old English and unchanged, and that its opposite even carries all three senses too.
1adjectiveunevenNot level.
“The table rocked from side to side because the floor was uneven.”
2adjectiveinconsistentInconsistent in quality.
“The album is uneven, with a few great songs and many forgettable ones.”
uneven is a quality of irregularity.
Old English unefen is un- plus even. Dutch oneven and German uneben are the same compound, and even has meant both level and equal since Old English.
Old English
unefen — unequal, unlike, dissimilar, diverse, irregular
Middle English
uneven
English, today
uneven
From Middle English uneven, from Old English unefen (“unequal, unlike, dissimilar, diverse, irregular”), equivalent to un- + even. Cognate with Dutch oneven (“unequal, uneven, odd”), German uneben (“uneven, rough, irregular, bumpy”).
Etymology from Wiktionary, CC BY-SA