What is the meaning of ˀ?

glottalization (i.e. a glottalized consonant or vowel)

a weak, fleeting or epenthetic [ʔ]

a graphic alternate to ⟨ʾ⟩

stød

a sonorant initial that pairs with a dark ( (yīn)) tone (ˀC)

an ejective consonant ().

A letter of the Cayuga alphabet.

A letter of the Chiwere alphabet, written in the Latin script.

A letter of the Sechelt alphabet.

Source: wiktionary.org