Sikhism has a doctrinal affirmation of Waheguru, instituted by Guru Nanak. This is the Gurmantar, or Guru's creed. Note the use of mantar here for creed: the Mool Mantra can be called the Mool Mantar and mean creed.
Wahe implies wonderful, magnificent and astounding and is an objective understanding of the majesty of God. Guru means God subjectively because it comes from Gu, darkness, and ru is from light (or lightness). So God here is both objective existence and subjective expression. God then comes fully to humanity through the Gurus, and is made real and experienced through this both objective and subjective state.
God is not as such described. Rather it is God as revealed coming through the light and word of Guru Nanak, God's manifestation. However, this is still the naming of God, or Naam, and this is dependent on Gurpasad, or the Guru's grace. Gurpasad needs delivery to manifest itself, first of all by the naming of God in saying Waheguru aloud, then saying Waheguru siliently in the mind, and then letting it work in the subconscious. To recite this continually and spontaneously is to engage in aware meditation on the name of God, known as Ajapajaap. This joins the person into the loving nature of God - God consciousness joins God. This is the nectar of Naam. It is transmitted by the Shabad, or divine word just as the Guru demonstrates Divine Light or Jyot (Guru Shabad, Guru Jyot are the essence of the Gurus passed from one to the other up to and including the Guru Granth Sahib: Guru Angad was so named by Guru Nanak because he had the same Ang or Self as Guru Nanak for the Divine Light and the same Shabad or Divine Word).
Source: Singh, G. K. (1995), 'Guru Nanak Dev Ji: Unique Revelation of God', World Faiths Encounter, No. 12, November 1995, World Congress of Faiths, 23-27.