red cap—
1. (UK) a military policeman:
- She used to take me to nightclubs tucked away which no officers or redcaps knew about.
2. (coll.) a railway porter:
- Why don’t you get a red cap to help you carry your bags.
3. the European goldfinch:
- Many birds seem to have particular names in these parts. Woodpeckers are called pickatrees, and goldfinches, red-caps.
red hat—
1. a cardinal’s hat as the symbol of the position:
- To receive the red hat he must go to Rome.
2. (UK Army) a staff officer:
- A number of very high-ranking officers were invited. …The visiting red hats were not impressed.