brass

brass /ˈbræs/ Brit /ˈbrɑːs/ noun
plural brasses
brass
/ˈbræs/ Brit /ˈbrɑːs/
noun
plural brasses
Britannica Dictionary definition of BRASS
1 
[noncount] : a yellow metal that is made by combining copper and zinc — often used before another noun
2 
: musical instruments (such as trumpets, trombones, and tubas) that are made of brass
[noncount]
[plural]
— often used before another noun
— see also brass band
3 
[noncount] : bright metal objects made of brass
4 
[noncount] chiefly US, informal : the people in the highest positions in an organization (such as the military or a business) — often used with the
◊ Brass is used with both plural and singular verbs in this sense.

(as) bold as brass

— see 1bold

get down to brass tacks

informal
: to start to discuss or consider the most important details or facts about something