Complicated or tricky; complex, difficult.
Of a part of the body, a tree, etc.: full of knots (knobs or swellings); gnarled, knobbly.
Of string or something stringlike: full of, or tied up, in knots.
Of an austere or hard nature; rugged.
Difficult to overcome, solve, or decide.
Contributing (especially if subtly) to discrimination (such as racism, sexism, homophobia, transphobia, or ageism).
Not settled, uncertain, of uncertain outcome; debatable, questionable, open to doubt.
a problematic analysis
A problem or difficulty in a particular field of study.