Meaning
The syllable Gam belongs to Ganapati in tantric practice, a seed sound held to carry his form rather than describe it. Ganapati joins gana, meaning a host or group, with pati, lord, so the whole line reads: Om, Gam, I bow to the lord of the hosts. He guards thresholds, which is why beginnings are placed in his care.
गणपति को नमन, विघ्नहर्ता।