'Weaker' in the Bible

One man’s faith permits him to eat everything, while the weak believer eats only vegetables [to avoid eating ritually unclean meat or something previously considered unclean].

But even more, those parts of the body that seem to be weaker are necessary.

Likewise, ye husbands, dwell with them according to knowledge, giving honour unto the wife, as unto the weaker vessel, and as being heirs together of the grace of life; that your prayers be not hindered.