tumbleweed: any plant that breaks away from its roots in autumn and is driven by the wind as a light rolling mass
weed: any plant that crowds out cultivated plants
sphenoid fontanelle: the irregularly shaped area on either side of the cranium where the frontal bone and the anterior tip of the parietal bone and the temporal bone and the greater wing of the sphenoid bone meet; corresponds to the pterion when bones have ossified