The green costume

Original fiction extract.

From the bus, I caught a glimpse of someone in a green dragon costume outside the sports centre. Then a delivery van blocked the window and we turned into the next street. I told my sister I had seen a dragon. She asked whether it had wings, but I had not had time to notice. At home we found a notice for the charity fun run. The photograph showed a long green tail, though it did not settle the question about wings.

Use your own words to explain what the word “glimpse” means in this extract.