This is the 3059th most frequent Russian word.
иду
"Iду" means "I go" or "I am going" (on foot).
The word 'иду' here is a verb in the first person singular, meaning 'I am going' and indicates an action of going or walking to a specific location.
Я иду в магазин.
I am going to the store.
'Иду' in this context is used in a metaphorical sense to describe the approaching rain.
Иду дождь.
The rain is coming.
In this sentence, 'иду' denotes a habitual action of walking a specified distance.