See also:

U+24C5, Ⓟ
CIRCLED LATIN CAPITAL LETTER P

[U+24C4]
Enclosed Alphanumerics
[U+24C6]
Daltonian symbol for platinum

Translingual

Symbol

  1. (electricity) water pumper
  2. (chemistry, obsolete) platinum ("platina", Daltonian symbol)
    Technically, this should be typeset as a black 'P' in a red circle.
  3. (phonetics) an unidentifiable/indeterminate plosive
  4. (engineering, GD&T) projected tolerance zone, a prediction of the final dimensions and locations of features of a component

See and ◌⃝ for uses of a letter inside a circle.