The term MECCA TREKKER is composed of two words, 'MECCA' and 'TREKKER'. The first word, 'MECCA', is a city in Saudi Arabia that is considered to be the holiest site in Islam. It is the birthplace of the Prophet Muhammad and the destination of the annual Hajj pilgrimage. The second word, 'TREKKER', refers to someone who goes on a long journey or expedition, usually involving walking. The crossword solution for this term is HAJI, which is an Arabic word meaning 'one who has made the pilgrimage to Mecca'. Therefore, MECCA TREKKER can be defined as someone who has made the pilgrimage to Mecca.