uisge = water an t-uisge = the water As you pointed out, "tha an t-uisge ann", is used for "it is raining". Here "ann" is followed by "am". "Ann an/am" = in So, this would probably mean "the water is in a mug". As to whether it can also mean "it's raining in a mug", I'm not sure. One of the moderators can maybe put us right.