Abstract: A vibration resistant, energy efficient lamp (10) that is suitable for, for example, ceiling fan operation where vibration is always a concern. The lamp (10) comprises an envelope (12) of a suitable transparent glass, for example, a borosilicate glass, having a substantially spherical upper body (14) with a given diameter D, a substantially cylindrical waist (16) having a diameter W of about 38% of the given diameter; a neck portion (18) having a diameter N of about 31 to about 32% of the given diameter and a threaded base (20) having a diameter B of about 25 to 27% of the given diameter. The base (20) has a skirt portion (22) adjacent the neck portion having diameter S substantially equal to the neck portion (18) diameter N and larger than the diameter B of the base (20).