![1girl azur_lane bangs black_coat black_footwear black_hair black_legwear boots bow brown_eyes cannon coat code_t_(azur_lane) commentary_request dual_wielding eyebrows_visible_through_hair floating_hair full_body gloves hair_bow hair_over_one_eye high_collar holding holding_sword holding_weapon jacket katana long_hair looking_at_viewer lowres miniskirt pantyhose parted_lips pixel_art pleated_skirt ponytail ribbon rigging skirt solo standing sword takao_(azur_lane) thighhighs torn_clothes torn_legwear transparent_background turret uniform very_long_hair weapon white_bow white_jacket white_skirt zero2 rating:s score:7 post #3741536](/cdn_image/preview/fc/92/fc9234e40f7e629f3d6fa56468e376c0.jpg)
This tag indicates that an image exhibits a distictive pixelized style (e.g. jagged edges, dithering). This may be either intentional or as a restriction on the software used to render it. This is common in older GIF images as well as images meant to invoke game sprites.
Pixel art is almost necessarily digital art in a rasterized format, and as such is naturally mutually exclusive with traditional media and vector traces.
Different from oekaki which is a very specific concept.