The phonetic transcription of the word "Gillham" is /ˈɡɪl.hæm/. This surname can be broken down into two parts: "Gill" and "ham." The first part is pronounced with a short 'i' sound (as in "pill") and a double 'l' sound. The second part is pronounced with a short 'a' sound (as in "ham"), followed by an 'h' sound that is not pronounced separately from the vowel. Together, these sounds form the distinct pronunciation of "Gillham".