GOV.WALES uses cookies which are essential for the site to work. Non-essential cookies are also used to tailor and improve services. By continuing to use this site, you agree to our use of cookies.
Definition: Strwythur mawr ar gyfer hysbysebu yn yr awyr agored. Fe'u ceir gan amlaf mewn mannau lle bydd llawer o bobl yn pasio, fel gerllaw ffyrdd prysur.