What is the meaning of ?

Died, dead.

Used to indicate a (second) footnote.

Extinct.

Used to indicated a destroyed type specimen.

Used in scorecards to indicate the wicketkeeper.

Check.

crux critica, crux desperationis, used around a corrupt part of a text

A pointing mark in Anglican chant, used in the margin to indicate a nonstandard place where a verse should be sung with the second part of a two-part chant; typically used for the final verse of a psalm with an odd number of verses.

Hermitian conjugate of

Source: wiktionary.org