Honeycomb
Honeycomb turns up in 2 fields: concrete, aviation. Here is what it means to the people in each one.
Honeycomb in concrete
Patches of bare, loosely bound stone with open gaps, left where paste never worked in around the coarse rock.
Shows up when forms are stripped as patches of bare stone with open gaps between, usually at the bottom of walls and columns, around congested rebar and at form joints that leaked paste. Causes include poor consolidation, segregation, harsh mixes and placing too fast. Shallow honeycomb is chipped out and patched; deep honeycomb near reinforcement goes to the engineer for a structural repair.
"Stripped the column and it's honeycomb at the base where the stinger never got down past the ties."
Honeycomb in aviation
A lightweight core material made of hollow hexagonal cells sandwiched between face sheets.
Honeycomb is a structural material featuring an array of hollow hexagonal columns, typically made from aluminum, fiberglass, or aramid fibers. When bonded between two thin outer skins, it creates a composite panel with exceptionally high stiffness and very low weight. Aerospace manufacturers use it extensively in floorboards, control surfaces, and engine nacelles to reduce aircraft mass without sacrificing strength.
"The inspection revealed water intrusion and delamination in the honeycomb core of the elevator."