Size and shape; aesthetics

большћй рћт a large mouth
большерћтый large-mouthed
огрћмный рћт an enormous mouth
ширћкий рћт a wide mouth
NB The word џзкий is not used to render an equivalent of the English expression "a thin mouth"; тћнкие гџбы "thin lips" is used instead.
небольшћй рћт a small mouth
мђленький рћт a little mouth
аккурђтный рћтик a small, nicely shaped mouth
очертђния ртђg the shape/outline of the mouth
лќнии ртђg the shape/lines of the mouth
Лќнии ітого ртђ бІли замечђтельно тћнко изћгнуты [Л. Толстћй, Войнђ и мќр] The lines of this mouth were extraordinarily finely curved. [L. Tolstoy, War and Peace]
кривћй рћт a crooked mouth
косорћтый having a crooked mouth
(глубћкие) склђдки у ртђg (deep) lines around the mouth
Мнљ бІло бћльно вќдеть глубћкие склђдки у её ртђ. It was painful for me to see the deep lines around her mouth.
пџхлый рћт (or пџхлые гџбы) a full mouth, full lips
NB The words пћлный "full; plump," and тћлстый "fat; thick" are not used with рћт, though these adjectives are used with the word гџбы "lips."
нљжный рћт (or нљжные гџбы) a soft mouth, a tender mouth; soft lips, tender lips
чџвственный рћт a sensual mouth
красќво очљрченный рћт a beautifully shaped mouth
красќвый рћт a beautiful mouth
очаровђтельный рћт (or рћтик); прелљстный рћт (or рћтик) a charming mouth
NB The two expressions shown above are often used to describe a woman's or a child's mouth.
некрасќвый рћт an unpleasant-looking mouth
безобрђзный рћт a misshapen/ugly mouth
щербђтый рћт a gap-toothed mouth, a mouth with some teeth missing