This is the 906th most frequent Indonesian word.
riau
"Riau" refers to a province in Indonesia, but in a broader sense, it can mean "disordered" or "messy" in Indonesian.
In this sentence, 'Riau' is used as a proper noun referring to a specific geographical location, namely a province in Indonesia.
Pulau Sumatra memiliki provinsi bernama Riau.
The island of Sumatra has a province named Riau.
Here, 'riau' is used in an informal or archaic context to mean unsteady or rickety, describing the condition of an object.
Lemari buku itu tampaknya riau sekali saat dipindahkan.
That bookshelf seems very rickety when moved.
In this case, 'Riau' specifies the regional variety of the Malay dialect, naming a cultural or linguistic characteristic associated with the region Riau.