What is the meaning of ʔ?

glottal stop; The symbol itself is referred to as a glottal stop or gelded question mark.

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

A letter of the Comanche alphabet.

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

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

A letter of the Kwak'wala alphabet, written in the Latin script.

The first letter of the Lushootseed alphabet.

A letter of the Nuu-chah-nulth alphabet.

A letter of the Okanagan alphabet.

A letter of the Sechelt alphabet.

Source: wiktionary.org