What is the sound of the a in washing?

The "a" in "washing" is pronounced like the short vowel sound /ɒ/ in British English or /ɑː/ in American English. It is a relaxed sound, similar to the "a" in "father" in American pronunciation. In phonetic terms, it is typically represented as /wɔːʃɪŋ/ in American English and /wɒʃɪŋ/ in British English.