Ad lib is an abbreviation of the phrase ad libitum, which is Latin meaning "at one's pleasure." When you ad lib you are improvising or making something up without any preparation.
A bib is a garment usually worn by babies. It is worn around your neck and protects the clothes on your chest from getting dirty.
A crib is a small bed for a baby to sleep in. Cribs usually have bars on the sides so the baby doesn't fall out and hurt themselves - and the bars also keep older babies from escaping! Cribs are also known as a cot or cradle or an infant bed.
A jib is a smaller, triangular sail at the front of a sailboat. Some larger sailing ships have more than one jib.
Something is ribbed if it has a raised pattern on it or markings that look a bit like ribs.