Steamies are trains that run on steam. They are old-fashioned trains that make a choo-choo sound.
Steamies are often seen as charming and nostalgic.
Examples:
The kids love to watch the steamies go by.
The steamies are very loud.
I saw the steamies at the train museum.
The steamies puff out lots of smoke.
The steamies look like they're from a storybook.
The steamies make me think of old times.