Transliteration: gnam lcags kyi thog rgod
<phrase> "Meteoric iron (kind of) lightning bolts". The kind of ཐོག་རྒོད་ "bolts of lightning / very strong lightning" that Tibetans believe is the cause behind the appearance of གནམ་ལྕགས་ meteoric iron artefacts. Tibetans consider that these artefacts appear just under the surface of the soil after (not always immediately but some time after) the bolts of lightning.Note that this term mean does not "meteor showers with lightning" which is a Western way of thinking. In the Tibetan mind, it can either mean 1) generally, "lightning that is so strong, unbelievably powerful" or 2) specifically, "the very powerful type of lightning that causes the appearance of these meteoric iron artefacts". The understanding here is a Tibetan understanding does not fit with the modern Western way of thinking. Essentially it is talking about Thor's bolts of lightning here: super-charged zaps so strong that they have magical powers. E.g., [CSG] དགོང་མོ་ལ། གནམ་ལྕགས་ཀྱི་ཐོག་རྒོད་ཆེན་པོ་ཞིག་བྲུལ་ནས། གཟིམ་ཁང་གི་ཐོག་ཁང་དུ་ཕོག་པ་དང་། ་་་་གཟིམ་ཁང་བཀས། ཐོག་མངོན་སུམ་མདུན་དུ་འཁྱིལ་ཀྱང་། དྲིན་ཆེན་ཆོས་རྗེ་ལ་གནོད་པ་ཅི་ཡང་མ་བྱུང་བས། "that night an exceptionally strong bolt of meteoric-iron lightning came down, struck the roof of the house, cracked open the bedroom, and landed right before the kind dharma lord but he was not harmed at all". Note how the term is being used to refer to an exceptionally strong, single bolt of lightning.
It is used metaphorically too, to indicate the extraordinary strength of something. In these cases it is very much like the Western way of thinking of "high voltage", exceptional electrical power. E.g., in a text: མཛད་པའི་ཕྲིན་ལས་གནམ་ལྕགས་ཐོག་རྒོད། "the activities of the enlightened actions of (the great guru), meteoric-iron thunderbolts..." or "the high voltage activities...", etc.