Definition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT.Greek plak-, plax flat surface.First Known Use: 1842.efinition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT. Greek plak-, plax flat surface. First Known Use: 1842.
A tree pruner is a class 1 lever. The fulcrum is where the two blades cross, and the load is what you are cutting. The effort is applied to the two handles.
tree trunk. pirogue - A canoe made from a tree trunk. tree ring - Any of the concentric rings of the cross-section of a tree trunk, representing a year's growth, or the layer of wood produced by a year's growth in a woody plant; also called annual ring. block - Derives from Middle Dutch blok, tree trunk.